After launching proclaim, initially, videos would play, and showed. But after sitting for some period of time (i don't know how long), the videos no longer play. or if you don't start it right away, as I normally do - after a period of times, the video slides turn into static images, and they are no longer able to play.
my workaround this morning was to launch proclaim and start after rebooting the computer. by the end of the service, any videos in post service slides were not playing.