[tor-relays] Loss of Guard and HS Dir flags

I currently run 3 relays, across different servers and today I noticed that one has now lost it's Guard and HS Dir flags.  What's surprising is that this particular relay has the highest Bandwidth and Consensus Weight of all 3 and has not been restarted for over a month.

The stats for all 3 can be found with:  OhNoAnotherRelay

I know that just running the relay is the important part and caring about what flags it has is a side issue, but I'm just interested in seeing why this has happened.

Cheers.