Adjust the latch

The bobbin endplay is determined by the latch adjustment.  To adjust the latch, loosen the screws holding the latch to the base, but only enough that you can slide the latch back-and-forth.  Don't loosen the screws so much that the latch moves freely; just enough so that you can slide it. 

Slide the latch toward the front to reduce the bobbin endplay, or towards the back to increase it:


Check that the bobbin endplay is about 1/16 to 1/8" (about 1-2mm):


Once the endplay is correct, tighten the screws.  The latch may move a little when you tighten the screws, so you may need several attempts to get it just right.

If you cannot get the adjustment perfect by sliding the latch, you may need to adjust the vertical position of the strike.  This is a very sensitive adjustment, so don't attempt it unless you must.  Adjust the strike up to reduce the endplay, or down to increase it.  You will almost certainly need to readjust the latch after adjusting the strike, and it will probably take a couple of tries to get it perfect.