LR develop module slow, locks up, freezes
I have created a brand new catalog for 2019 with only 200 photos in it. The catalog files are stored on my local computer (brand new 15" macbook pro, 2.9 GHz Intel Core i9, 32 GB 2400 MHz DDR4) and my photos and backups are stored on my business dropbox account. However, when I go to the develop module and use my presets, it basically locks up. LR is incredibly slow, sometimes freezes, and is essentially unusable. I'm noticing it more with some photos I imported from my iPhone (so they are .jpeg) but don't have enough photos to fully test the RAW format.
I see a lot of posts about LR being slow. Is there a major issue going on, or does LR have problems with JPEG files vs. RAW files? I'm really confused. I used LR for years (before 2018) and never had these problems.
I have the latest version, classic CC, all up to date.