I found the AliExpress LED bulbs also used on the wagon and decided to put them in the 84TC also.
Tried the driver side first. The socket did not like being disturbed and I think the centre contact got sort of squished in, and didn't spring back out, so now no bulb will light up in it without pressure applied. No cornering lamp on this side until I replace the socket or otherwise get it to make contact.
Decided to try the passenger side, despite high probability of the same issue happening. Success.
Will root through my collection of junk to see if I have the appropriate weather-tight version of that socket but I'm not too optimistic.