Took this standard xmark apart, polished all the engagement areas and replaced the spring that does the pull weight. Used the spring off of an automotive air stem valve as the big "fix". The factory spring is only like a 1/4" long, and when you back out the screw trying to reduce pull weight much under 3 or 4 pounds (on this one), I'd run out of spring tension inside and get random sear engagements and pull weights. Wasn't sure where the spring was or how it worked, so that's why I took it apart. WIthout taking the trigger apart, it can be removed from just unscrewing the adjustment screw out, fishing out the factory spring and replacing it with the valve stem spring (*cut mine at least an 1/8" longer than the heavy factory spring). Got alot more range of adjustment due to the longer spring, in much lower weight range......right about 1.5# now. No slam fires, no drop fires with this one! My sear engagement screw absolutely would not free up. Tried heating several alan wrenches cherry red, putting heat into the screw......nothing. Tried a red hot soldering iron, nothing. Tried a pencil torch, nothing. Gave up on it, not much creep at all(polish job may have helped that), just coulda used a touch less engagement. Still plan on replacing, but for now, it's so much better than the 6 pound "feel" it had. Overtravel won't budge either. This may or may not work on others.
