UK BFT bollard tripping rcb when returning to its extended position. Why is this?

[Thrusten]

Hi everyone
I installed a BFT bollard about 3 years ago. It's been a very reliable piece of equipment however today it has started to trip the rcd when ever it returns to its extended position.
It allows me to switch the rcd back on, it won't trip until the bollard is activated goes down allows the vehicle to pass and then on its return journey up it gets approx 3/4 of the way and then trips. I have tested the resistance on the bollard, there is nothing preventing it from traveling further, physically that is. I believe its a electrical problem, but where to start any thought??

 

[littlespark]

Not sure how these things operate, but I expect a limit switch near each extreme position to tell the motor to stop.

Have you got a wiring diagram, or make and model?
It might be microprocessor controlled, and therefore a replacement board might be needed.