I have numerous MKV files that use E-AC3 (DD+) format for audio. All of these files playback correctly with Plex. In my new Z9X Pro when I play back these files the audio has a constant rate stutter and are unlistenable. I have changed every setting (Auto/Raw) I can see to change and nothing fixes the issue. I am running the latest firmware as of today. I also just reset the player to factory and the issue still remains. Other audio formats such as Atmos, DTS, etc work correctly. My processor is the Emotiva MC1 and works very well with my Sony OLED TV, Oppo 203, etc.
Basically the stutters issue was fixed on last firmwares. Are you playing it from a NAS? Wifi or Ethernet cable? Take a look to this thread on this line http://forum.zidoo.tv/index.php?threads/occasional-jerky-choppy-playback.97341/
I am using a NAS which has worked well for 15 plus years with Plex, Roon, etc. 4K and Atmos, DTS, etc work fine. It's just E-AC3 DD+ that have this issue.
Well, I completely forgot about this! Mind like a sieve... Anyway, I get exactly the same as you with a Z9X Pro - broken audio. I tried my own h.264 and h.265 E-AC3 5.1 files here on a Z9X Pro and they play fine, so it's got to be something to do with the compliance of the file.
I use Vidcoder which uses the Handbrake back end. Typically I just copy Dolby E-AC3 without transcoding. My file plays in Plex streaming to all my TVs and Android, etc. Plays in VLC just fine. Until proven otherwise, it's a Zidoo bug. Hopefully they will see this and fix? Or, how do I submit a bug report.
It's a tricky one - some players are more tolerant of poorly compliant files, some less so. What happens if you play the original file before encoding?
The original file is just a rip from the Blu-ray so it should play just like a Blu-ray. I don't know why this matters? The vector that seems to be the problem is the combo of H.265 video and E-AC3.
It very much depends on how it was ripped and with what - I use MakeMKV followed my MKVToolnix exclusively and quite honestly have never had any issues at all. I used DVDFab years ago and that was beset by problems, hence why I don't use it now. There's no intrinsic issue at all with h.265 and E-AC3.