I have experienced 2 independent MacPro cases where ProRes timelines would crash all the time with Blackmagic cards.
External video OFF, and the problem was gone.
No they have AJA cards and never had any problems.
Maybee because the AJA cards have a framebuffer.
Something is def going on here lately with Blackmagic.
I like the Blackmagic stuff and i never had much problems with the cards, but lately AJA is my first choice.