Quicklook Takes Forever to Load Images/Videos

Working on an external drive. Quicklook slows to a crawl when trying to pull up images or videos. Works perfectly fine in Safe Mode. I have trawled the running programs and processes in Normal Mode but have not been able to pinpoint what is slowing it down.

I have tried to run EtreCheck, but it also gets bogged down (loaded for two hours before I cancelled it) with whatever is happening when checking software.