Hi mrbanjo
I once had the problem "I should get an Extraball" - sometimes I got it (Extraball-Relay pulling-in) - but very oft: I did NOT get the Extraball (relay not pulling-in). It was a connecting wire broken-off a solderlug - wires are stiff - stay in place (connection) - a bit of shiver / shaking - the broken-off end of the wire moved a bit to the side --- no connection - a bit of shiver shaking - the broken-off end of the wire moved back - connection again ...
See the JPG - "my green lines" are just a possible way the stuff is wired in Your pin --- check all the wiring of "wire-in-the-pin-color-yel+blk-yellow-mingled-with-black".
Maybe You must use an 24Volt-SteveFury-Test-Light mounted like I show in the JPG. Greetings Rolf
0Paul-Bunyan-Work-01 (resized).jpg