/ban_all fails to ban certain users with cache error

[viganogabriele]

The /ban_all command does not work for some users. The command fails with the error: 'Not a valid userId or username not in our cache'.

This may occur due to bot downtime or cache issues. Affected usernames have been shared separately.

Steps to reproduce:

1. Attempt to run /ban_all on a specific user
2. Command fails with cache-related error