Source and Program Monitor Freezing after a minute or so of editing

I can't find a good answer to this, and after spending a ton of time on chat yesterday, still not resolved.

I have the most tricked out Macbook Pro, so the comptuer isn't the problem.   I do work off of Lacie External drives.  It was suggested to do all of my editing off of the internal storage, but with 4k files, that wouldn't last long.   

Anyone?   

I've deleted 3rd party plugins, I've uninstalled, reinstalled, but still, program and source monitors freeze pretty quickly.    

I almost have to look at Davinci or something else soon if I can't resolve this.    I would be so grateful for any suggestions.