Apple Photos App Not Exporting Edited Photos Correctly

What system version are you running. It's working for me.

Try the following;

1 - As a test launch Photos with the Option key held down and create a new, test library.  Import some photos and test to see if the same problem persists. Does it? This tells us if the problem is limited to your current library or is more wide spread.

2 - Log into a new, basic, admin user account, Set up users, guests, and groups on Mac,  and repeat #1 tosee if the problem persists. This tells us if the problem is limited to your user account or is system wide.

How are you exporting? What edits are you not seeing in the exported version?

Try file>export (NOT export unmodified original) - that will always export the edited version as jpg, tif, or png.