[shunut]

If you push the trigger and push on the back of the bolt (no air connected) will the bolt go forward freely or does it feel like its tight and takes a lot of effort?

Could be a couple things, battery problem is definitely one of them. You could try shimming the solenoid. Just put a penny, nickle or dime behind the solenoid, between the flat side of the piston that is in the solenoid and the body of the trigger frame. The coin should stay in there with the grip on and you shouldn't have any problems. Test each size coin to make sure you aren't over shimming which would do the opposite of what your problem is now.