Premiere Pro CC 2017 Freezing after 2 minutes of use

Hello all,

I am running a mid 2012 MacBook Pro,

2.3 GHz Intel Core i7

16 GB 1600 MHz DDR3

NVIDIA GeForce GT 650M 512 MB

Intel HD Graphics 4000 1536 MB

Premiere Pro CC 2017 keeps turning to the swirling beachball of frustration after I do any more than 2 minutes of work consistently and "application not responding" appears. I changed my settings to clear the media cache, turned off auto save, allocated more memory for Premiere Pro, moved the media cache and database. That all was a stop gap that took no more than 20 minutes of work to bring back the same problem.  I am working off of a LaCie 4Tb rugged hard drive through USB, most of my footage is 1920x1080,  with a small smattering of 4K footage due to my drone that only appears infrequently on the timeline. I tried updating to Premiere Pro CC 2018 but it was even worse.

So I am trying to diagnose where this problem is coming from, my computer, the program, or the hard drive I am working off of? It could be something else entirely and that is why I am asking here. Thanks for any help!