can you please elaborate on the " improperly adjusted trigger bar spring. "
trigger bar spring hooks ride out of the trigger bar grooves where they should be. Mostly riding on the outside (closer to frame) edges of the grooves instead.
Then a user must "fix" it with dental picks and similar tools. I think a good way of doing it is to adjust using a mag catch spring screw, not to pull on hooks. If you pull trigger bar spring hooks, TBS "arms" will stay in the same place anyway, so you did nothing because you will move arms (and hooks consequently) with the magazine inserted if TBS arms are not close enough to the frame.
If a person wants the job to be done as it should be: mag catch spring screw out, clear it from Loctite, new spring in, adjust it with screw (hooks 1mm from frame to ride in grooves), stake mag catch spring screw.
I got the feeling CZUB is economizing on working hours where they can.
English is my 2nd to 3rd language, I don't know how express myself better in specific tech terms. I hope you understand.