First time I hear of a problem. Server is still running smoothly as far as I can tell. Which Electrum version are you using?
2.5.2 portable. The wallet in question is pretty old, with thousands of addresses and transactions. There is no limit that could be hit?
And since force download did not work, can it somehow happen that empty labels are uploaded so that downloading does have no effect? Otherwise i wonder how the server can't find labels for it anymore.