OK, well my Morley problem has been mostly fixed.
The issue was caused by the pots in the hand held units!
Voltage would spike and dip as the pot was advanced causing bad running.
The fix could not be more simple.
Carefully pull the knob off and under you will find a nut that holds the pot in place, undo this nut a full turn or more (but not so its lose)
Then refit the knob.
The issues is caused by changes in temperature, meaning the nut is overtight which causes the wiper on the pot to lose contact with the track.
There you go, one of the hazards of having tight nuts!