Getting code CD-7 just before contactor comes in, once contactor is in the fault goes.

Every now and again I get AD-3 AD-4, I've found if I turn the truck on with the key switch the fault occurs more often than not, If I leave the key switch on and plug the battery in the fault doesn't appear.

I've swapped the drive controller positions and the fault was fixed for a while, customer has reported it is faulting again although I haven't been back to the truck yet.

Any help gratefully received