photo editing in os 10.13.3

As you can see no one else is reporting this problem so there is something with your system that you need to resolve

As a test hold down the option key while launching Photos and create a new library - does it have the same problem? If so try the same test in a different user account

and download and run Etrecheck and post the results here

LN

partially on the bottom left of the screen until it rights its self and the crop screen has random editing moments, sometimes taking a proportion of the photograph off.

I noticed this weird behavior starting with macOS 10.13.2. It happens occasionally for panoramic photos that need straightening. when it happens, I restart Photos, and then the cropping will be back to normal. But I never noticed, that the crop tool will take a long time to launch. Are you using iCloud Photo Library and "Optimize storage"? Or, are your photos on an external drive?