Somebody help me, I can't work like this.
 
Abby Road Plate Reverb, TG12345, a few others.  If I turn turn them off, the project plays back smoothly.
 
Lots of pops and little skips- jittery as hell.  Tried changing the buffer size, the sampling rate, MCCSS, plugin load sharing, 64bit precision engine, share drivers with other programs; all these parameters don't seem to have an effect.
 
This has been occurring with Focusritee Scarlett interface, Audient ID14, and RME Fireface USB.  
I also tried 32 bit Sonar and 64 bit.  Nothing seems to work.
 
Some projects the plugins function without problems.  Others it's just no fun to work on them because it's snap, crackle, pop.
 
Anyone been here?  Any suggestions?
 

I have the Abbey Road plates and am running a Scarlett 2i4. I haven't noticed any problems that seem specific to those.
Have been starting to work with VSTis) in Kontakt Player and have had to play with buffers to address cracks/pops. Sounds like you've tried all the things I'd try. Next thing I'd do is uninstall/reinstall plugins one at a time and test after each to see if you hone in on the problem child.

Have you updated Waves Central lately?  Maybe try a complete uninstall, manually delete any Waves folders, then reinstall.
 
I'd also do a VST reset/rescan (Always a good idea when adding any new plugs).

I fixed the problem.
I googled "optimize windows 10 for music production" and followed the instructions provided by the focusrite step by step.
Unfortunately, there's no way to know which thing fixed it, because I did them all (except messing with Windows Defender).
Here is the page i used:
https://support.focusrite...or-Audio-on-Windows-10

Should have mentioned that I am using a new computer, but it didn't have this issue for the first few weeks.  
I was sure that it was a Waves issue because it was specific to certain plugs, but I guess not?
I should go open up a few more projects before I claim victory, eh?

good info....glad you got things sorted.  I started having issues with waves, but a simple reboot put things back.