Hi I had a similar fault on my triac this week where the carousel would only travel 1 way when it should of retracted the solenoid just exhausted air out. I stripped the solenoid and found it was traveling further one way than the other, I figured it to be the internal clear seal was damaged, these have been discontinued so I just fitted a similar sized O ring now all is fine. I figured that the 2 clear seals are there to limit the solenoid piston travel. The cost of a replacement solenoid is getting on for £100. Hope this helps

Ade