Problem with audio drop outs in the passthrough mode on kodi depends on minix firmware only. Note that you cannot install a 64-bit version of kodi on marshmallow. Question is why? Although the U9-H hardware is 64 bit, the firmware is not. And that's where the whole problem is! I tried install beta FW (Nougat 7.1.2), then 64 bit of Kodi (or WBMC, if you want) and problem with sound disappeared. Unfortunately it is beta and this contains a lot of other bugs. Example: adaptive picture refresh rate does not work, network outages occur when waking from sleep and some more. In the other side, the Nougat 7.1.2 solved problem with playing videos on websites, especially flash. My suggestion: If possible, everybody let's return all this Chinese scrap back to the manufacturer. The manufacturer is unable to make a working firmware. They have our money, and we have her scrap named U9-H.
Problems with audio dropouts over passthrough can quite literally be caused by any number of different factors, from the actual audio codec itself or its source (i.e. who ripped it?), through to any external cabling or audio hardware also in use. The variables involved are countless from one end user's set up to any other!!
As the term "passthrough" also implies, the raw audio stream is simply sent on to
your external hardware for the decoding to happen. If you're experiencing drop outs, guess where they're likely to be caused? If everyone that used passthrough with Kodi &/or the U9-H was having these issues, you can be certain steps would have been taken to resolve them by now. However, the vast majority don't!
Ergo, passthrough audio dropouts simply are not caused by Kodi with the stock FW008 on the U9-H at all.
My suggestion
would have been avoid the ranting, & jumping straight over to a beta ROM before even checking with other community members if they've experienced problems under similar conditions, or with a similar setup or audio hardware to your own.
Of course, that's pretty much too late now that you've stepped on your own dick!
Personally, I now have absolutely no interest in determining if you're using HDMI or TOSLINK, discussing other specifics, or helping you in any other way at all either!
You're on ya own fella
! Enjoy it whilst I enjoy perfect audio passthrough with my U9-H
.