and well written pool software

Heh well that's a bit of a sore point cos Kano keeps expecting me to find something and fix it, but any possible cause for the recurring issue that might be in the software that I postulate doesn't seem to change the behaviour so I keep blaming hardware... but I keep looking anyway. Chasing ghosts indeed.
Kano, throw the server on some other hardware? mem/prime/fur test the old hardware?
Could one of my IP's have been banned from the pool and website? I haven't been able to access the website from home and my miners here are rolled over while my gear that is offsite is plugging away fine.

I randomly ban stuff that is either doing a large blockchain download from bitcoind or that is repeatedly getting failures on the console
... and other reasons

PM me your IP and I'll check why.
My manual ban script ... I add a comment every time also why I did.
Also, if you use an IP address hiding service and someone else uses it also and (fails) to hack at the pool, that IP can be banned also and I then wont unban it.
you doing an ip range? or just selected ips? (just wondering if you're covering dynamic PIs, I've been on the wrong side of a stick when someone else has been banned off a site and my IP was in the same range)