So my girlfriend's Lightroom just started doing this funky thing. In Library mode, it runs fine, but the second you enter develop mode, the entire OS freezes. The only way to get any response from the computer is to force shutdown using the power button.
GPU acceleration is turned off, and we also tried turning it on. We are on MacOS 10.14 Mojave on a 2015 retina MBP with 16GB of RAM and 2.7GHz Core i7. The Lightroom on my laptop is the same version, same software version, but a different spec (2018 MBP, 2.9 i9, 32GB) and I do not have the issue at all.
We turned on GPU acceleration a few days ago and though that had something to do with it, but we also tried turning it back off and when the problem persisted, did a full removal and reinstall of Lightroom. The issue still persists, any help is much appreciated!