Thanks, Mike, for pointing out this one, which is a close second to “Translate Server Error.”

The
English is clear enough to lorry drivers – but the Welsh reads “I am
not in the office at the moment. Please send any work to be translated.”

When officials asked for the Welsh translation of a road sign, they thought the reply was what they needed.

Unfortunately, the e-mail response to Swansea council said in
Welsh: “I am not in the office at the moment. Please send any work to
be translated”. (BBC)