Can't Add App to User with Developer Role

I am unable to add apps to users with the developer role under "Users and Access". I click on the apps for the user, select the apps I want to add, and click "save." But I get an error shown at the top of the page "There was an issue granting apps for 1 user." That's it. No other context about whatever the issue is at all.

All the users that I am trying to add apps to have multiple apps already assigned to them.

Can't Add App to User with Developer Role
 
 
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