How to prevent automatic upgrades of KODI on Android TV box



Hi,
I have a, not so versatile, chinese ANDROID TVbox (X88King, Android 9.0.0, hardware OK, software bad, and the manufacturer never supported any updates) 
But it does quite well for the purpose I initially baught it:
Playing content from my NAS.
I have SMB enabled on the Synology NAS and I very happy playing movie content in any format with HDAudio passthrough to my AVR receiver.
Now KODI seems to upgrade itself now and then, which is normally a good thing, but with build 21.0.(21.0.1) it got (I think famous):

“One or more items failed to play. Check the log for ……etc”  error.

Especially when trying to play DVD folders with video_ts files in it.
I tried to fix it with some tips from from internet but was fed up.
I know that more people have this error, I don’t want to spent hours trying to fix it (unless somebody has the golden tip here) but anyway:

I uninstalled KODI V21 and manually installed an older “MATRIX” version (APK file download install via USB key) which is perfect! 
Created the shared folders again and back in business

Now it happened already 2 times: 
I startup KODI, screen turns black for a short moment, and it is back again on version 21 with the above mentioned error….
I checked Apps settings in ANDROID, I checked all settings in KODI, and I do not see any setting that prevents auto update.
(option would be to disconnect the TVBox from internet somehow)

How can I prevent KODI from updating itselfHuh

Thank you in advance,
Kind regards, Wim