Recorded audio turned into distorted buzzing after VariAudio


I was trying to fix the pitch in my recorded parts with VariAudio. At first, it is fine but after a while it turns into distorted buzzing (even if I unplug the Amp simp and return to clean tone). I deleted distorted parts and record it again. It only takes a while before it becomes distorted again. I have not encountered this issue using Cubase Pro 12 until now. I wonder anyone would happen to know the solutions? Attached is the wave form after I copy and paste the tracks into other project.

I am not sure if it is related to my recent update on RAM, since which the DAW has become problmatic. Files become corrupted easily and shut down in the midst of bouncing and unable to open. The PC runs normally thoug and problems are only encountered while I am using Cubase.