I was trying many things like:

• changing php version for the site
• changing php version for cronjob
• changing ffmpeg.exe with newer version
• and more, I cant even remember all the things I tried

but none of them solved the issue with duration of video not shown on the site.

Then I renamed /plugins/ffmpeg/ffmpeg.exe to ffmpeg.exe.bak (to have it there for backup) and I've created a link to system's ffmpeg version located at /usr/bin/ffmpeg in a /plugins/ffmpeg/ folder....

And voila:

I am happy now and Christmas parties can begin.... 😉