This happens when you use audiosnap and creat transients.   I reported this ages ago and go nothing back.   I also do what was suggested above to some succes 10 min 200 chgs but it only helps so much.  When it get really bad I turn of autosave and make sure I save constantly on my own.  Did you enable audiosnap in your project?

  I rarely use audiosnap anymore. After comp editing clips, if I still have timing issues I find Melodyne editor to be more intuitive.
  Both of these features cause autosave to do its thing constantly. Unless the values are set high. Which will inevitably lead to data loss.
  So I turn autosave off and use Cntrl-s after EVERY edit. Sometimes twice, maybe five times.
And every time I take a break, I save copy as... to a big usb drive.

Holy cow!  You step away for a few minutes and look what happens!
 
Thanks for posting guys.  I had thought of shutting the Auto Save off and now that I see others are doing it I might too.  If nothing else, when I'm in Melodyne.
 
Paul