[Chiumanfu]

Common causes of the bolt being thrown forward:

Bad QEV. Qev's can become gummed up over time. Especially if you over-lube or use loc***e to seal the threads. Unscrew the QEV from the breech and hold the bolt back with your finger. Air up the Ion and make sure there is air coming out the threaded port of the QEV. Unfortunately most qev's can not be serviced so if it's gummed up, you'll have to replace it.

Debris blocking the sail output of the noid. Little bits of bumper oring and globs of lube can block this port from supplying the pressure to push the sail back. A sticking armature can also cause this. Service the noid, making sure to clean out all lube and make sure the tee-fitting oring is good.

The furthest post that the solenoid coil is soldered to is shorting against the frame. This will cause solenoid to exhaust the pressure holding the sail back and the bolt will stay forward.

Bolt Guide Seal or Bolt Main Seal worn out or unlubed. If either of these two orings are leaking, the sail might not build up enough pressure to overcome the pressure in the dump chamber.

Bolt Stop Inner Seal damaged or unlubed. May physically stop the bolt from moving back especially if the oring is getting hung-up in the air pass-through channels on the bolt. Less likely, but still possible culprits are the Bolt Rear Seal (Tail) and the Bolt Tip Seal (SFT). If these orings are cut or deformed, they can cause the bolt to jam.

Detents could be getting pinched between the bolt and breech. Make sure your detents are not stretched thin.