When opening video files, even if very small / short, I got a minute of waiting with the Alert "Loading Media, Please Stand By...".
I use most frequently mp4, but it happens with different video formats. The very same files do open instantly with VLC, QuickTime Player, Preview. Having to wait a minute makes the use of the player pointless.
I'm using Screen on a brand new MacBook Pro 16-inch M3 Max with 64GB RAM, Sonoma 14.3 and Screen 1.4.14 (3195)