I access the forum using Tor.
I think this is the catch, I spent a lot of time on the forum yesterday and didn't get a single error. Although I get the forbidden error sometimes, but it's very seldom and negligible and I don't border about it. I always think that maybe the forum is under some sort of DDOS attack and it only persists for a little while.
BTW, I don't access the forum through Tor, I've also been on the forum for 3 hours now and had no issues, so I think it's has something to do with the Tor you're using, I'm on Edge browser.