Media Pending error when switching in and out of multicam

Occasionally when switching into the multi-cam mode. The "Media Pending" error fills the screen. The media is obviously there as it plays from the timeline when not in multi-cam mode. I give it time (minutes) to find things and sometimes it works sometimes it doesn't. Running 3 camera sources. All source material on SSD drives. A combination of MXF and Prores footage. All HD. This is a new issue with recent beta builds. Duplicatable on a MacBook Pro and on an iMac.