Have you disassembled and cleaned the finger plunger parts ?
Stretching the plunger spring slightly often helps with lever closing issues.
Any issues with the extractor on the bolt?
Otherwise, check to see if the carrier is bent or there are rough areas on it. Polish without removing stock (400-800grit) on any rough/burr areas.
See if there are any issues with the locking bolt surfaces.
Check the end of the lever that goes into the bolt to make sure there are no burrs, etc.
