To get a better understanding of the problem you are experiencing we need more information from you. The best way to get this information is for you to upload logs that demonstrate your problem. You can learn more about how to submit a useful support request here.
Depending on the used skin you have to set the settings-level to standard or higher, in summary:
enable debug logging at settings->system->logging
reboot the OSMC device twice(!)
reproduce the issue
upload the log set (all configs and logs!) either using the Log Uploader method within the My OSMC menu in the GUI or the ssh method invoking command grab-logs -A
publish the provided URL from the log set upload, here
Thanks for your understanding. We hope that we can help you get up and running again shortly.
Oddly enough I do get sound when from these files when plugged in direct to the TV - passthru enabled or not.
No sound from them when connected to the Oppo.
If you just want to play the files without having to modify them or your setup you might have some luck setting your Kodi audio settings to 2.0 channels and in passthrough enable AC3 transcode.
That doesn’t work either.
Oddly enough I can use avidemux to copy the video and remux the audio to different formats and all play fine on the computer but still no audio with the Vero 4k+ connected to the Oppo 105.