In C6M4, in the second video, all the cameras were messed up, and it was impossible to see the characters. I set it to static, and it seems to be working fine.
It's not a huge amount, but there are quite a few messed up cameras; you can see them in the list of changes where the messed up cameras were.
It doesn't seem to trigger dialogues; as an alternative, you could insert the start of the video at the beginning of the relevant map for testing.
What's the command to launch dialogue scenes from the console?