Try the following and report back:
1 - As a test launch Photos with the Option key held down and create a new, test library. Import some RAW 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). Then test again in your current library.
2 - Log into another admin user account, Set up users, guests, and groups on Mac, and repeat #1 to see if the problem persists. (This tells us if the problem is limited to your user account or is system wide).
3 - lastly boot into Safe Mode (How to use safe mode on your Mac - Apple Support) by booting with the Shift key held down and test in your primary library. Reboot normally and test again.
NOTE: Safe Mode boot can take up to 10 minutes as it's doing some system cache cleaning, volume verifying and directory repairing.