Thanks again to all.
... So I punched in from there, thinking maybe the system is trying to keep the earlier parts of the song. That worked for about another 60 measures. It it helps diagnose this, the song is at 130 BPM.
In RB the possible issue you mentioned can be tested.
If it is indeed the disk trying to write while reading at the same time, in the Audio Prefs area is a place to change your 'Temp Audio Directory', which is where incoming data gets written. I regularly record 8 tracks at a time without issue.
I usually use a separate drive for writing incoming data so the read drive does less work with less interruption.
Drives can be a bottleneck historically.
Also, try MME even if just temporarily. It may give clues.
Maybe something else is tapping on your ASIO driver and RB is having to share it.
If you were doing anything that needed ASIO, and this makes a difference, it could still be anything from driver issue to the VST(i) that got changed when switching to MME.
You can always very easily switch back but it reveal a clue as a quick test.