After a bunch of trial and error I believe I figured out the issue. The photo I was working on was an HDR of 3 LR enhanced images so the file was about 680 mbs. The final size of the edited .PSB file was 6.5 gbs and I'm guessing Luminar just doesn't like large files. I did some testing and it looks like if I disable all of the layers above the sky replacement smart object, delete the smart object, create it again, everything works just fine. Honestly that doesn't make any sense to me... Why would making a new smart object be any different than changing the values of an existing one?