Photo 5 video import, but dont play all video

hi there,

so the problem is this ... with mac os catalina when in photo version 5 i create a project slideshow... i put my image then some videos when i click play the video start i see photos but when there is a video i can only see some seconds 2 ... 3 .. but for example the video is 15 seconds??? i cant understand ... i use for example vintage stamp like template ... if i use standard theme no problem ??? is incredible ... i spoke with support apple and they said maybe system bug .... now i have update but nothing ... :( i have make a test with my original library then with a new library ... nothing to do .. the video are cut!!!!

ideas?

thanks