That was a nightmare.... I had a dud contact on my (cheap as chips) rotary switch.
I thought I was going mad, the logic had gone all twilight zone!

I now have a lathe that works in forward and reverse.... CHEERS GUYS!
It is just a simple case of moving the two jumpers / bus bars through 90 degrees on this motor (or adding a switch to do just that)

Clarke Motor M80 BL4
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Cheers for the link M_C
I had seen a few similar those but that was a good one!

Driftspin: dmv?
I was going to pull the motor out and measure all the winding wires but I thought I would give it one last run through as the logic seemed to be pointing to an strange anomaly or fault somewhere.