Hi ,
CB6000 lbs. truck. You didn't mention CBE so we will assume it has an engine either GM/PSI or Toyota. 2 potential causes.
1. Posible dirt particles caught in the steering orbital. We would not typically recomed that this can be flushed out and due to safety reasons, we would recommend it is replaced.
2. Priority valve on the steering orbital is sticking. You could try to flush it to se if it will free itself, but most likley require replacement
Part no "CPS00020" is the steering orbital and priority bvalve in a single unit.
Alternatively you can submit a technical query via the combilift web site. Go to the bottom of the web site and select "Technical Support"
Link is https://warranty.combilift.net/technical-support-form/
Combilift Technical Support is free to use.

Thanks Richard