I've tried connecting videos with a wide variety of formats and decoders. All videos either slow down or do not play at all. And also a one-second freeze occurs during playback.

Videos freeze and slow down.

All ingame videos are freeze or skipped

Perhaps, but at least the intro didn't want to load. Lol

I am unable to reproduce slow video on any machine I have access to.  I tried running the COAS introduction video Title.wmv using an Intel HD 4000 with Win7, a Radeon R3 with Win10, a Radeon R5 with Win10 (all laptops) and they played the video at 200 FPS.  I also tried a GTX 1060 with Win10 and it also plays at 200 FPS, with no lag or freezing.  So I don't know what the issue is, because I don't experience it with any of my computers.

Pretty sure that here xxxLEOPARDxxx meant not video slowdown or FPS loss exactly, but noticeable freeze/microfreeze when video is getting loaded by the game.

But I am not exactly sure if anything can be done about this.