Could the forum be causing the errors? Perhaps it's time to tag @theymos in the discussion and see if he has any ideas.
It is possible that he changed something in the server recently, which may be blocking too many requests....
I was taking a look at this problem today, I couldn't solve now.
I still think it's the proxy's waiting time for the server.
Maybe @theymos can give the proxies more waiting time for requests to the Bitmover website.
I don't know, it's just an idea.