Thanks for that.
My eyesight is not what it was but the joints definitely look not touching/joined to my eyes.
However, when I re-attached the plate initially the problem was gone!
But I then discovered I could get the problem to re-occur if I wiggled the volume pot.
So presumably, even though they look not touching or joined when the plate is off, they are close enough to make contact when the vol pot is wiggled against the screwed down plate.
If so, I need to resolder those two joints, keeping them apart. Is that likely to be correct?