User account not saved on page (in users field)

I have a users field on a page and for some reason there is one specific user that isn’t saved when saving the page, i. e. I add the user (to all others), save the page and all seems well. But if I reload the admin page that user isn’t there anymore. I checked all file permissions in the user’s files and they appear to be similar to all other users.

I’m out of ideas. Is there anything else I could look for?

Hm, do you have a hook in place that does things when you save a page? What does the field setup look like (blueprint)?

Huh, interesting …
I’ve changed the user’s e-mail address in the past and when I changed it back to the original one it worked again. Also, trying this further, I can’t login as the user with the new e-mail address; it says the account can’t be found. If I look at the account’s index.php file I clearly see the new address there, so the file is saved properly. Is this address saved/checked somewhere else, too?

Does it only affect this one user account? Then I’d delete this account completely and recreate it, maybe something was messed up at a certain point.

OK, I think I’m a step further: it looks like the problem occurs if an email address has uppercase letters in it. If I create a new user and enter an email address like it will convert it to lowercase automatically. However, if I then edit the user profile and change the email address to include uppercase letters again, it saves it literally. Whenever an email address has uppercase letters, I can’t login – this seems like a bug to me.

Yep, that’s somehow not really consistent.

Are you using the latest Kirby version?

Yes, I just updated to version 3.5.4 yesterday.

I can actually reproduce the issue. Could you create an issue with the steps to reproduce, please?

Done: User account email addresses with uppercase letters cause issues · Issue #3305 · getkirby/kirby · GitHub