One thing to look for is maybe the stock is improperly inletted in the trigger area. If there is even the slightest pressure somewhere, it could cause some trigger problems. Are you
sure there is no contact between the stock and the trigger where there shouldn't be? Being there could be some contact inside the stock, it might not be easily visible.
If it turns out to be the trigger, maybe consider having a custom trigger either from Timney or Rifle Basix installed. The trigger might have a problem when it is in the stock, or might be defective. I would think it better to try installing a new one. If the problem still persists, give the factory a call.
-Patriot