1. Have to ask the obvious, are you running a check valve (usually coupled with remote lines)? Look at the link below. Make sure everything in the valve is clean, free of debris, and all orings are in good shape. You might just want to do a rebuild to be safe. A picture of your setup would help; we might see an accessory (e.g. on/off) that could be the culprit.
The link will show what parts you need. As you stated, there's a special quad oring at the top of an e-mag valve, but I don't think that is required in your setup.
What is the length of the on/off pin and trigger rod? Is there a credit card thickness gap between the back of the trigger and the trigger rod when pressurized?
Be careful. Wear eye protection at a minimum. Sounds dangerous disassembling a pressurized marker.
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