Sim, change out all the orings and slide the bolt back and forth whilst the engine is out, feel if there is any restistence.
After you inserted engine back into marker, check for any leaks in breach and back of marker, also check for leaks around the noid area (making sure the noid is screwed down properly). This can be done with the frame off the body when you air up.
If the problem persist, then send it my way, and i will swap parts out with mine ie noid, board, full engine to see where the problem lies if any.
( i have all necessaries to do all the testing )