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Can you post up the schematic?
If it has a separate relief for that ram? It is possible it could be leaking causing the creap.

The other thing I have seen in my many many many ram repairs is sometimes the ram tube can be streatched aound the piston in a over pressure situation.

This will present as a barely perceptible ...

I dont think it would be a relief valve as those control maxumim pressure from the pump.
When there is no control input there is no (or shouldn't be) pressure being supplyed to the ram.....the only...