Login Failed but

I’m fairly new to Nextcloud, but I do have it up and running. Managed to work through all the setup items until I have a nice check mark on my setup, an A+ on the security audit, have put up GeoIP on my reverse proxy.
I do notice however that I get a random "Login failed: " notification from time to time in the logs…which is weird because, if I didn’t see the notification in the logs, I wouldn’t know about it since I’m able to login just fine.
Anybody know what this is about and how to correct it. I want to put up Fail2ban but I don’t want to inadvertently lock myself out due to this message in the log.