Cyber Rgobo homing issues

Three of our cybers (a CX, a CL and an SV) have trouble homing the rotating gobo wheel.
Rehoming never seems to fix them, but very slowly driving the rgobo channel through the rotating range often resets them properly.
Fiddling with the spring plunger on the rgobo wheel hasn't really helped - I wonder if there's a spring plunger associated with the rotation mechanism that I might have missed?
It feels like the rgobo wheel and the gobo rotation are not playing nicely together.
Any thoughts?

Cheers,

Scotty.
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