[Solved] Episode preview pictures not showing (MySQL)

Hi everyone,
I have this strange issue with the preview pictures from episodes of my TV shows. My setup is as follows:
Raspberry Pi3 with and MySQL database on my NAS. Latest version of OSMC on there.
On my Android device that connects with Kodi to that same databse, all the pictures can be seen. On the Pi, not all pictures are showing. Even after refreshing. The pictures are there, otherwise I wouldn’t see them on my Android device.

Any idea how I can troubleshoot this or correct this issue? Please let me know if I can attach more information somehow. Maybe debugging on certain areas?

Thanks for any input available.

Try enabling “extract thumbnails from video files”

Thanks, but I seem to be missing that option in Settings - File List. I’ve got it on expert mode btw.

Edit: found it. Thanks. Going to try this.

Yes, that did the trick! Thanks a lot.