A photo that hopefully shows what I am saying. This is an assembly I am making from scratch and is not balanced at this point.
You can see the lower spring and how the top sear spring could, and is known too, slide off the side if the screw is loose.
The front through bolt holes verses the rear which can not pass through because internal parts are in the way. If the sear is well fit in the trigger frame, then too tight of a front bolt puts a side load on the the sear causing it to hang up. Cure...don't tighten the screw so tight.
Visible is the sear nose, front curved portion, that engages the hammer notch. The top spring keeps down pressure on the rear of the sear, keeping the front in contact with the hammer for positive engagement when the hammer is cocked.
You can also see how the cocking or set trigger spring if putting too much downward force on the set trigger, or more likely made improperly, then the trigger arm will set too high holding the sear off the hammer. Balancing keeps the trigger arm low enough and lets the sear float against the hammer but with enough tension to trip the sear, countering the hammer main spring tension holding the sear in place in the hammer,.....when intentionally fired.
Bob