Cloudflare has gotten stricter. I have experienced such error in other websites as well including bitcointalk. Although too annoying cases have been less of an occurrence -- I typically just do one captcha per session.

For the most part, I think it has to do with our IPs getting flagged. Are you on VPN? if so, try to turn it off or play with other servers (of course, only if bons permit VPN usage. Another thing you could try is to turn off your internet router for a couple of seconds and turn it on after because in some cases, this changes your IP address from your ISP.