[Ben Kolff]

I don’t know if this solves your problem, but I had a problem like this and managed to find a simple solution. Here’s what I did…

The culprit was a mismatched RT preference setting (which can be changed by clicking the little “RT” pulldown menu that’s on the far left side of the timeline window.) For some reason, I had defaulted that setting to “Safe RT,” when it wants to be set to “Unlimited RT.” That worked for me but I have no idea why. Let me know if this helps!