One problem is slop in the slot on the trigger plate. All my single trigger T/Cs have that lost motion to one degree or another. Material must be added to make the slot narrower. Then remove it as necessary to more closely fit. The width of the trigger plate must stay the same or it wont fit in the guard housing. I think T/C left this loose because this clearance is dependent on the stock.
There may be a way to run an adjustment screw from underneath, so you could assemble the lock and trigger then adjust the wiggle out. Maybe a spring to close the gap [but not drop the sear]. Ill be working on this.
In any event, be careful. If you cant do it safely, then leave it alone.
Good Luck, P.A.