5 Second Delay between moving sliders and image updating

I realize people post about slow Lightroom performance in here all the time but I've tried everything I've found in these threads (I think) and I'm still having major issues.  There is sometimes a five-second delay between moving any slider and the changes appearing on the image.  I noticed this after the 12.2.1 update but even when I reverted back to several version earlier the problem persists.  I've disabled the graphics card, I've cleared old previews, I've set my camera raw cache to an external drive with tons of space and given it a 20GB limit, and I'm editing with just smart-previews  Anything else I can try would be amazing!  

I'm working with a 15" MacBook Pro 2017 with 16GB of RAM 250GB of internal storage.