The page linked to by the "overloaded" alert on my relay's Relay Search page mentions using MetricsPort for troubleshooting, but it provides no information on how to actually use it. I posted about this issue on Reddit and no one has replied with a viable guide to help me out, though one user was able to find a page showing at least the syntax for MetricsPort. I also reached out to network-report@torproject.org and have not received a reply. I found discussion about the implementation of MetricsPort on the Tor Project github but it would be nice if the Tor Project officially documented this, especially since it is suggested in the guidance for resolving this problem.
At any rate, my relay is 4.5 years old and I've never had a problem with it being overloaded until now. It is on a Raspberry Pi 4 (4 GB) and that doesn't appear to be anywhere near maxing out CPU or memory usage. The only change I have made is putting it behind a pfSense hardware firewall, but the firewall itself is not maxing out in CPU or memory usage or even storage.
So, any help that anyone can provide is greatly appreciated! Thanks in advance!