? Please upload a screen shot - a full screen image showing left-center-right panels open in Develop with the crop tool selected. When Lr (or other apps) display odd behavior it's a good idea to fully power cycle your system. Shut everything down and restart.
Consider resetting the preference file. The preference file can get corrupted, leading to buggy behavior. A corrupt preference file will survive updates, upgrades, re-installs. Resetting the preference file is Adobe speak for deleting it. After it is deleted, Lightroom Classic will create a new one upon launch. Side effect is settings in preferences will reset to defaults.