I have been struggling with this issue on and off for a while and had run out of workarounds to combat it, so I am glad I discovered this thread. I, too, have done the maintenance items suggested numerous times but what finally made the difference was deleting audio EQ filters. How and why they got corrupted just sitting there I don’t know, but they were just temp until I do the final mix (for which I will export OMFs to PT anyway) so it’s no huge loss.
Thanks again to everyone who offered advice and I hope other’s problems have cleared up by now, too.