Today I switched from OpenLP 2.x to 3.0.2.

Everything works fine, except the presentation of Media (Video and Audio).

Presentation starts but then it stops immediately (after less than a second).

VLC media player is installed on the machine.

Any hints?

a month later

Reported elsewhere as well. Someone suggested leaving a black section at the end of the media, but I have 100's of recorded video clips, so that is not really possible.

Can you check the log file for errors?

https://manual.openlp.org/troubleshooting.html#i-have-been-asked-to-email-a-debug-log-where-do-i-find-this