Your trigger adjustment scheme is pretty simplistic - the screw changes the depth of sear engagement and any looseness in the thread fit, dirt or debris inside could make it not repeatable. The Loctite is a good idea but you may want to clean all the trigger parts. Looks like the BSF 50 shared a simple trigger design with their smaller models, and only the 55 and up used the unitized multi-lever trigger. There is no "HW version" of your gun - the two were competing manufacturers - but in terms of model lineup position, your 50 is closer to a 30 than any other HW. Don R.
Can the trigger group be changed out to something more adjustable? Quote