remix of the flux dispenser which does not work. Piston stay on the same position, does not push piston forward. I realize that problem are grooves on piston pusher, they are not deep enough and they are symmetrical. So I designed asymmetrical grooves piston pusher. This works fine.
Print it vertically (already added big stabilizing base) with layer 0,1 mm, so shape of grooves is good and detailed.
Added STL and SolidWorks file.

remix of this:
https://www.thingiverse.com/thing:5490223