As a consequence of files being in use by open programs, the locker may not be able to unmount and close the LUKS volume.
This is a security issue, as some users may want automated guarantee that their sensitive files aren't accessible when they are AFK.
I do not know how to easily solve this problem without forcefully killing programs. That's definitely not ideal, and can lead to data loss depending on the workload.
Perhaps, making use of
i3-nagbarbefore manual lock is an intermediate step. It could warn the user to close programs preventing the unmount operation. Alternatively, it could be used to notify the user after they unlock.Unless I'm mistaken, I think that this isn't able to be fully automated without significant drawbacks at edge cases, and as such, it is up to the user to practice good opsec and not run a workload that frequently prevents unmounting in this fashion.