How to Change the Yamaha Advanced Setup to DTS Mode 2 (after above firmware update)
(The Default DTS Mode is 1 - no need to change it if your player bitstreams DTS OK)
With AVR off, Advanced Setup is done by holding the "Straight" button under the front cover, then push 'main zone'/power button. Advanced setup info shows only on the AVR's display, not the TV. (See manual for details.)
Using the right side of the "Program" horizontal rocker switch, step though until the the DTS Mode option is shown. (It's just after the 4K Mode option.) Pressing "Straight" button changes the Mode setting. (While in Advanced Setup, you may want to backup your configuration settings.)
  I wish the new DTS Modes was an option setting for an Input instead. That way you could set Mode 2 just for the input of an affected player instead of a global setting. Or at least have DTS Mode as an option in the normal (on screen) setup options. No info yet if mode 2 has any downside for players that were not affected by the DTS bitstreaming issue, but if not why have 2 modes? (I saw a post about the Denon update fix, but it didn't mention an options setting.)

Using the RX-A3050 with 1.77 firmware, I confirmed the "PCM" issue with DTS discs played from Sony BDP-CX960 changer (expect same from higher end BDP-CX7000ES model) and Sony BDP-S1000ES (same era player, likely BDP-S5000ES also affected). And I've seen a (2008 model IIRC) Sony BDP-S550 owner report this problem after getting a new DTS:X Yamaha receiver. (Same AVR fix required, see above update info and how to change the DTS Mode setting for Yamaha models with later firmware update.)

Despite the player being set for bitstream, it was sending PCM to the DTS:X updated receiver. Playback of Dolby TrueHD discs however were still correctly bitstreamed to the RX-A3050. Since those Sony players have been out of production for years (and no firmware updates since 2012 as of this post date), I wonder if we'll ever see a firmware update to fix this from Sony. (Again, it was not an issue before the DTS:X firmware update for receivers, and not AVR brand specific.) It may be related to a bug in the AVR update's EDID for DTS, but not sure why it's only affecting older Sony Players based on tests so far - the 2014 BDP-S7200 tested OK. I have my doubts they will address it if only a few older players are affected, unless they agree it's a bug, and enough owners complain perhaps.
(Update: Denon did release a fix for some AVRs in late June 2016. Yamaha did in late July.)
Granted, single disc blu-ray players are cheap/easily replaceable (1080P at least), but the changers are not. (Nobody makes them anymore.) I have a 7000ES changer still in the box from when they blew them out several years ago for a small fraction of list price. (If Sony ever does update them I wish they'd also fix Gracenote, but that's another story.)

Here's a list of the Blu-Ray and UHD players that tested OK
(DTS HD/DTS:X discs bitstreamed correctly with v1.77 firmware RX-A3050)

• Panasonic DMP-BDT500 (1080P) firmware 1.63
• Samsung BD-F7500 (1080P) firmware 1021.0
• Samsung UBD-K8500 (4K/UHD) firmware 1003.1 and 1005.0
• Sony BDP-S7200 (1080P) firmware M21.R.0164
• Magnavox NB530MGX A (1080P), made in May 2009 (never updated)

I had hoped to find some setting option in the affected older Sony players that would solve this, but no luck so far. They were both correctly bitstreaming DTS-HD before the receiver's (v1.77) DTS:X firmware update, so I'm not sure there's really any fix for this without a firmware update for either the player or DTS:X receiver.
(Update: See top of page for notes on later firmware updates to address this from Denon and Yamaha. The Audio/HT page post on July 28th, 2016 Yamaha Firmware Updates for 2015/2016 models includes download link, list of changes/new features/improvements and FYI about Yamaha's "Additional information about DTS-HD and DTS:X playback" PDF with details on how to set the DTS Mode in Advanced Setup. Default is DTS Mode 1, you only need to change it to Mode 2 IF you have a blu-ray player affected by the DTS bitstreaming bug noted above.)

Other DTS:X Related Notes/Tips:
With the DTS:X Update, the Yamaha's Audio Info screen (remote's On Screen->Information>Audio Signal page) will show if there's any DTS:X objects in the encode. If so it's listed in the Input section "Channel" info - example: "7.1.4 + x Object(s)". (x being the number of objects present.)

I saw someone claim that 4 overheard (or height) speakers were required for DTS:X, but that's not what I've experienced using a 7.1.2 setup - only 2 height speakers. (Later plan is to either add 2 rear heights (and 2ch amp to drive them) for 7.1.4, or just use the rear surrounds for height instead for a 5.1.4 config.) 4 overhead/heights (2 front/2 rear) would be best, but DTS:X (and Neural:X) worked without rear heights. (Interesting that when I ran the "DTS Sound Check" in the Audio menu of "The Last Witch Hunter" DTS:X disc with this 7.1.2 (front heights) setup, a test of the left/right Rear Height speakers was heard - using the base L/R rear surround speakers. (Despite AVR set for front heights only and the "Virtual rear presence" speaker option was NOT enabled. I double checked that setting again after hearing the L/R Rear Height test played.) BTW: I later read that 11.1 DTS:X test was made to use Height speakers, which is said to be why when AVR is set for Overhead (or Top) vs Height the Height tests playback also using the base front/rear speakers.

DTS Dialog Control Feature (not standard):
When DTS:X was announced, I was excited to see the "Dialog Control" feature, where dialog level could be adjusted separately. (Not just boosting the center channel or a frequency range (e.g. standard 'dialog level' adjust), but the actual movie's dialog.) However it turns out that the DTS Dialog Control adjustment option is only enabled IF the DTS:X disc was encoded with that feature. Disappointed that to date, it seems no DTS:X movie discs have been released with that option enabled. Hopefully mixers will include that in at least some future DTS:X movies, as it's one advantage they have over Dolby Atmos. (Atmos had a much earlier start, with far more (and better) titles released so far.)

I didn't test with 2 channel sources but early reports from Denon/Marantz owners mentioned distortion in the center channel with upmixed stereo sources using Neural:X. (There may have been some other related bugs as well.) If this also happens with the Yamaha, I'd just use the other upmix options if desired. (In addition to Neural:X, this Yamaha series has Dolby Surround (DSU), PL IIx Movie, PL IIx Music, PL IIx Game, Neo:6 Cinema and Neo:6 Music.)

And btw, if you don't have any/many Dolby Atmos or DTS:X discs, this Aventage series can apply Neural:X or Dolby Surround (aka "DSU", part of Atmos upgrade) upmixing regardless if the disc is DTS or Dolby audio format. Yamaha also has many DSP modes, which are adjustable (including via touch screen with the AV Controller App) for room size/sound 'bubble', level of effects, etc. on later AVR models. (One of several options not available on my older RX-A2000.)

I've seen some users say they prefer the Yamaha DSP modes like "Adventure", "Sci-Fi" or "Spectacle" for specific movies over using Dolby's DSU upmixing. There's also several concert/hall/expanded DSP modes for Music but I rarely use them. (I avoided all DSP modes originally, but later found some useful after experimenting.)

Overhead vs Height Speaker Configurations:
Some DTS:X users are reporting that unlike Atmos, DTS:X works best with Height vs Overhead Speaker configuration. For Yamaha users, you can have switchable setups for Overhead and Heights. (Assuming your height speakers are close to the ceiling, worth trying to see how they compare.) You copy your speaker configuration settings (default is "Pattern 1") into "Pattern 2" and edit the copy so you have 2 different configurations - Pattern 1 set as overhead, Pattern 2 as heights. You can then switch from Overhead to Height settings by changing the Pattern used without repeatedly digging deeper in the menus. (This also allows you to have different speaker levels, YPAO mode, etc. for each pattern.) And you could use the "Scene" function to assign the different patterns for quickly switching between them for Atmos/DSU or DTS:X/Neural:X playback, using the Remote Control Scene buttons or the Yamaha AV controller App. (See PDF user manual for more info on Patterns and Scenes.)
   I've always liked Yamaha's dual Pattern option, very useful in my opinion. It allows you to make a copy of your complete configuration for experimenting with different setup/settings options (including speaker levels, distance, number of Subwoofers, crossover points, YPAO mode, etc.) while preserving your original setup/settings in the other pattern. (And easily switch back to the original for comparison or if you're not satisifed with changes.) I've used it for easily switching from single to dual subwoofer setup for instance. (The "Advanced Setup" options run using the buttons under the front panel cover (info is shown on the AVR's display) also has an option to "Backup" (or restore) your receiver settings. Handy to have a backup before you make major/multiple changes in case you want to revert back.)