There might be problem of that small motor , attach photos of the motor location where it gets fitted i will suggest you another motor according to available space
It checks the position of paper to start printing from the edge you can remove sensor from bottom of the head carriage and emulate it as the images and diagram shows which i have sent to you
Mechanical relay creates spark when ever they get trigger which is ok for small dc current but AC heater creates huge spark as they consume above 1000 watts i dont know why those stupid Chinese guys use Mechanical relay for this much of load there is some problem with there engineering
Well ok but i dont think that full size flapper will work perfectly it just pushes the film n we dont want that
We want the whole force at single point