Have one of these units with a creeping extra-dig ram. First capped off the ram and checked for leakage. All ok. Next went through solenoid valves and replaced them due to one faulty unit. No change. Checked check valves , burst protection valves and still creeping .Some suggestion that the main valve block could be fractured internally- anyone heard of this occurring.
The extra-dig function on my older 214S is a separate block, next to the excavator block. It has two relief valves, one on top and one on bottom. This was an auxiliary build on my machine. Newer machines may have all functions in one block, but I would assume your extra-dig function also has reliefs. These may be the culprit. How are you troubleshooting? Are you using a hand pump and pressure gauge? I, too, am having creep issues with my JCB backhoe. I am waiting for a hand pump to be delivered to more accurately diagnose my hydraulics.