My A1 Mini has made a clicking sound with two different extruders fitted. If you remove the nozzle, you find (3) 3mm machine screws holding the mounting plate. If you remove those, the plate can be shifted to show the back side and (4) smaller (2x6mm) machine screws. When I checked my A1 Mini, two of those screws were missing :-0, the third was loose and the fourth was hoping for a miracle :-). I noticed another post (thanks: Synchro777 ) that explained that this loose nozzle plate can explain poor z calibration and first layer problems which I had as well.
BL Tech support referred me to this wiki: A1 Series First Layer Print Issues - First Layer Too Low, Hotend Moving | Bambu Lab Wiki.
This describes: The 3 screws fixing the hotend heating assembly are M3x10mm; the 4 small screws at the back are M2x6mm (with flat gasket and spring gasket).
I had not seen it when I did my repair and went with M2x5 machine screws and thread locker, (M2x5 SHCS Machine Screw (20PCS) - AA150). Fingers crossed it holds.