Premiere Pro 2018 keeps crashing -- sequence importing / media cache problem

First off, while cleaning my Mac OS X (10.12.3) today, I moved Premiere Pro's Cache and Media Cache Database to my external hard drive, in the hopes that I could free up some space on my desktop. Admittedly, some of my footage comes from veeery long clips (some 2 or 3 hours) so my caches were eating a lot of memory.

This last step in my own project involves importing several sequences together from separate projects -- initially this was working, although the source files were taking up time conforming and performance was slower. but now, every time I try to add the third or so sequence, I get a window saying Premiere Pro needs to quit, then it crashes. One thing: the Cache + Media Cache on my desktop seems to have wiped, but I made a manual copy of the caches on my external in case I need to mess around with one. so maybe this is the result of Premiere Pro getting confused about which Cache location to refer to? Would it be best to have caches on my desktop or should I be able to manage them completely on my external if they're allocated correctly? Should I delete all existing cache folders, desktop and external, and designate them somewhere new on one of the devices? Either way, whenever I try to bring this sequence into the new timeline Premiere Pro shuts down on me. Working on a deadline here and I would suuuper appreciate some help.