cybre.space users: this appears to be due to the cybre.space web server taking too long to respond and returning a 504 / timeout error. if you see this happen, it might mean the server is just processing slowly and will eventually submit the post! (looking into why it's taking so long, but this should help you avoid accidentally submitting duplicates in the meantime)
@haskal digitalocean is definitely failing their SLA, but hetzner has been basically fine til now aside from an occasional short outage that kicked something of ours over. we are unfortunately getting what we're paying for, there, though.