Buyer beware of possible damage to upper - Elftmann Tactical ELF Service Trigger

Trigger felt good and worked well at the beginning, however as I ran more rounds through my AR, the trigger pull adjustment screw slowly backed out and interfered with hammer. This caused the hammer and BCG to slowly bind and stretch the rear take-down pin hole until the BCG would seize in buffer tube in retracted position. The only fix was to replace the upper to correct upper/lower alignment and put blue 242 Loctite on trigger adjustment screw(hopefully that will prevent further issues). With all the thought and engineering that went into such an expensive drop in trigger, I don't understand why the trigger set screw didn't have Loctite pre-installed or a lock screw to prevent back out. The instructions say to install Loctite on installation screws(that have a 2nd "locking" set screw also), but never mention putting ANY on trigger adjustment screw. A $130 lesson learned, putting the final "cost" of trigger to over $400.