Take the two triggers right out of the trigger plate and put the gun back together. Cock it and see if the hammer slips off of the sear w/o any help from the missing trigger.
If it holds,,then take a narrow metal instrument like one of those 6" machinists rulers and slide it up into the right trigger slot in the trigger plate and trip the sear. Get a feel for the engagement,,if it's barely holding or if it feels secure.
If it trips by itself or feels just barely engaged, then it's probably the sear itself.
If it seems OK, then it's probably the trigger blade causing the problem,,binding on the wood, etc.
Also check the sear nose and hammer notch. The hammer notch can load up with debris easily during a restock fit like this as it is cut quite deep to get a clean edge.
Also remember that even though the sears & triggers would seem to be farther apart w/the longer tang screw(s) the 2 tang screws can bend the tangs a tremendous amount in their final tightening and reallign the parts in such a way to cause problems.
