Media Offline issue in beta 6

Not sure why this is happening.. and I cant pinpoint if it happens in other modules, but when in color page, it seems like if I make a node edit, then use ctrl-z to undo it, or ctrl-x to delete it or something.. suddenly it shows media offline in the viewer. It stays that way until I restart Resolve. I did render out a video and the video is still there fine.. but in the clip it is gone. When I go back to the edit page, the media pane shows it fine.. but in the main window viewer of the timeline it also shows media offline.

Also when I use reset node grade.. the image comes back in the viewer.. but the node or nodes (added serial nodes) all show media offline image in them.

Just a follow up for the BM team... I cant even edit as this media offline issue strikes everywhere. When I try to edit text, or add any FX, it immediately goes to the meida offline in the viewer on the editing/timeline page, so I cant even see the footage now.

This is on a Windows 10x64, Nvidia 1070/8gb video card. Updated drivers, latest Win updates. 64GB ram.

Hope that helps.