The bolt springs are consumable items and do wear out. They need to be replaced from time to time. They slow down the reset action and will cause "temporary" bolt stick but the bolt will reset.
If the bolt stick persists such that the bolt will not reset at all, then the carrier size is too small for the oring you are using. If the gun fires but won't reset, shims aren't the answer. They might work in a pinch but all they are doing is allowing more of the air to leak out of the powertube reducing the opposing force such that the oring friction force plus chamber air force is less than the bolt spring force. You need to correct the real problem which is the carrier size.
Except for the Automag in front, its usually the man behind the equipment that counts.