Hi Doc
I didn't really get to test for loose connections on the tube socket, as I was distracted by the fact that one of the LEDs was out, and by wiggling the tube it came back on.
I guess that the centre pin connection is OK, as surely both LEDs would be out ? I need to check the other end of the LED that was intermittent, great idea with the chopstick!
I've ordered some LEDs incase that one is shot and I'll take another look next weekend, have a good evening, and I'll let you know the outcome 👍