SOLUTION: Conversion failed. The transcoder exited due to an error

Hi all,
I´ve arrived here having the same problem of the title in all my libraries…
This is my setup:
Device: QNAP NAS: TS-453 Pro
PMS Version 1.20.2.3343 (it happens also in my previous version)

I´ve tried to restart PMS, update to latest version (above) and also restart the NAS itself.

All without results. Getting in all items the message of the title of the thread.

If you need some log or test to do just ask me.

Thanks