2003 Haas VF4 Tool changer issue

We bought a used 2003 Haas VF4 a while back and are just getting around to getting to use it. We had a Haas tech come out and fix some issues we had with it and one that it was having has re appeared after it sitting for a few months. When I go to lower the tool changer pocket it pocket lowers but not all the way down and you can hear a constant air hissing noise coming from the air solenoid. When the tech was here he replaced several things trying to fix the issue one of them being the air solenoid but that didnt fix the issue. if you apply air directly to the air cylinder then it goes down without issue. but not when commanded. The tech wasnt sure at the time what fixed the issue but it must have been coincidental. Does anyone have any ideas I can try. Id really hate to have to pay for the tech to come out again since it cost about $600 for us to just get him on site...


Any help would be appreciated.