I have two flights coming up on TK in full fare Y that I tried to e-upgrade today. All I could get from the ICC was, "sorry, the request comes back 'technical error', nothing we can do, you'll have to keep trying later."
I have no status on UA anymore so can't escalate, but still, it is rather annoying.

Anybody else get this answer when trying to upgrade? The agent politely informed me that it happens 'mostly every time'.