Contactor drops out immediately

[Grumpy-b]

A strange one.
Van drove OK. After stopping the contactor clicks in and immediately drops out. Error light comes up. Turn off no error light, repeat same. Fault code if read before turning off is B1. This suggests the Mains lead is plugged in. It isnt. Door light off.
Connect Lexia. No faults, No door flap open, no cable plugged in.
It has been very wet so could be a stray voltage from some where.
Swapped calculator, no difference.
12v battery is fine and well charged. DC to DC working great. Contactor clicks straight away, just doesnt stay in. 12v isnt the problem.
Any ideas

Grumpy-b

[highend]

hmm.... maybe clean ground cable contact which is from left controller mounting to engine? or check it or replace?
btw. brushes received many thanks!