Yikes, saw your post and the feedback you got on the DUC… erk.. 

I sold off the Pro Tools shackles years ago because i got fed up from things like this.  So annoying.
Once I switched to PC and chose a Windows DAW, I never had an issue like this again. 
 I’m sorry I can’t help you and no one else has chimed in but should you find the solution, please report back to help others. 

I’d look at the cpu meters both in protools and in task manager and look for spikes. It could be a RAM, CPU, or disk issue. Are you using an hard disk or ssd?

you can try temporarily disabling some plugins and see if that works, and try restarting the computer. Also could try reinstalling the pluggins and or protools and the audio drivers.

it otherwise could have to do with which version of PT and Windows your using. 

sorry i don’t have an exact answer for you, this might take some trial and error.