Hi Brad. This certainly seems like a disk issue but hard to say. Have you opened a support case? There is a chance of corruption within PT but it has different symptoms than what you describe. See here (but it's a long thread):
https://duc.avid.com/showthread.php?t=405902
That's the only current show stopper corruption I've seen. There was another one related to imported material but I think it's been solved. Most other "normal" corruption can be solved by importing to a new session like you tried.
Let us know if you find anything out. You have my sympathy for lost work!