This appears to be someone/bot trying out common usernames in one of your apps. Unfortunately this is not too uncommon, but also not an a real issue if you have strong passwords. The requests will be rate-limited as well to prevent proper brute-force attacks.
The internal IP is associated to an app, it may or may not change when an app is restarted. However the ldap logs might indicate there are multiple apps configured to use LDAP. The port is actually dynamic per request, so that is the reason why it does not show in docker ps/inspect