Keysight U1241C Probe Detection Error

[backpedal]

Hi All

I have a Keysight U1241C DMM that is acting up:

when I remove the test leads and switch the meter on to anything other than the microamp range, it starts beeping and displays the "μAEr" warning.
In normal operation, this would only happen if a lead was inserted into the "μ·mA" socket to warn the user that the lead is in the wrong socket.

This is triggered by the banana jack bridging the two halves of the split terminal. I have disconnected the spring contact from the back of the jack socket inside the meter and verified that the fault is being caused by the physical jack, but cannot find the short, which I assume is happening inside the jack socket with my other meter. I have tried to clean the socket out and can't see any debris inside it so am out of ideas. Please see the attached pictures for a better idea of what I'm on about.

I have tried to contact Keysight but they refuse to provide me any information or as I am a hobbyist and not a business customer.
Has anyone experienced this issue or anything similar? Help or suggestions would be greatly appreciated.

Thanks in advance,
rjm