Both the Viewer and Canvas won't play the video while External Video is on. This is happening in two different projects: one is HD Prores and the other is SD Anamorphic. I also noticed that its also happening with standard clip in a sequence.

I played around with a few things and figured it out but its very odd I would never have thought this would have any effect. When I changed the Easy Setup to "Blackmagic NTSC - DV" instead of "NTSC-DV" it worked. Its odd that Easy Setup would have any effect on the playback of sequences that have already been created. What I read into this is that Blackmagic has their own version of HD and SD, and when their version isn't selected FCP can't display Internal and External video simultaneously.

Thanks! I did have that problem a while ago, sometimes it would work both internal and external, other times it wouldn't, Never quite put 2+2 together, I'm interested to know what they've done to make it work compared to the FCP presets.