Office 365 MFA Enabled Users and the Apple Mail app for iOS Concern

Our organization just rolled out MFA to all associates, and we've found the iPhone process to be ardurously difficult but have learned a few things:

Initially, iOS will ask you to re-enter your password and do a 2 factor authentication.  Usually we find (at first) the user must put in their AD password as normal and (in our case) authenticate with the Microsoft Authentication App.

Now, their account will typically stay authenticated for anywhere from 1 to 24 hours from that moment.

At some point, it starts asking for their password again but won't take their "normal" AD password.  Put in an Application Password.  iOS will still show that it's still not authenticated even if it "accepts" the Application Password, and we've found a reboot "finalizes" the process.

After the reboot, the iPhone is happy and the user can carry on with their stuff.

I'm not 100% sure why this works, but it seems to be what does work so I figured I'd re-post.