Lifton neuson 1001 dumper Hard steering

[sc15]

Hi there , I have a neuson 1001 high lift dumper which I have just been using on a job and the steering has gone very stiff ,as if the engine is offand there not power steering. The steering gets a little easier and harder depending if I lift /tip the skip up and down . Any suggestions of what this could be ?,so I don't end up stripping the whole thing apart was thinking maybe a priority valve , but I'm not to sure .
Thanks

 

[Vinpetrol]

I know I’m stating the obvious but it’s usually the best place to start ,
Have you checked the hydraulic oil level ?
Are all the rest of the hydraulics working ok ?
If they are , and the oil level is ok could you have squeezed a pipe going to the steering ram ?