Apple Macintosh Photos Application: Do others find this application unstable?

Hi - 40K is not an excessive library size, and no, I find photos to be rock solid, apart from some known bugs, none of which result in random crashes.

to help with diagnosis - can you answer the following?

• 
What version of MacOS did you upgrade from?
• Where is the library stored (System drive or external drive)? If external - what is the format of the drive?
• Is the library on a network drive or in some sort of cloud storage (EG Dropbox or NAS)?
• Do you use Icloud to sync photos?
• If so, do you have optimise local storage set?
• How do you backup your Mac?

It might be worth trying these initial checks:

1 - Create a new empty library and try with that library open (hold down the option key while starting photos, and click "create new". To switch back to your currently library afterwards, do the option key start again)

2 - Try booting in safe mode - does it still happen?

3 - Try creating a new user account and try when logged into that account.

These checks will tell us if the problem is system wide, or linked to a particular library or user account.

Also, do you use any "Cleaning" apps like CleanMyMac?

There have been reports that they can hose libraries.