Sewing machine vertical shuttle install - placing back bobbin case hook race locking ring

Placing back the vertical shuttle and this side loading bobbin on a sewing machine
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CHECK LIST reasons why the needle doesn't catch the thread or it's skipping stitches
bits of fabric trapped around the shuttle or under the feed dogs - remove shuttle, make sure you find videos showing how to place it back for your machine
bent needle
needle not fully inserted upwards or not inserted with the flat side the right way
thread passed the wrong way inside the needle eye (usually it goes from left tor right)
bobbin thread not inserted correctly into the bobbin
wrong type of needle or wrong type of bobbin
needle holder not secured at the correct position on the needle bar - usually it has a groove on the bar
bobbin case not fully inserted on the small shaft (must lock)
bobbin case ring holder not properly locked in place with the two small plastic tabs
wrong bobbin case - may not be compatible even between same brand
needle bar rotated - the needle eye is not parallel to the side of shuttle hook (loosen and rotate the needle bar, carefully not to move it vertically)
damaged tip of the shuttle hook after impact with the needle (replace the shuttle)
needle bar too low or too high https://rumble.com/v6kgx6a-needle-tim...
needle and shuttle out of timing (not synchronized) after sewing thick/stiff materials, also check for loose screw on the gears or on the rod connected to the gears https://rumble.com/v6kgx6a-needle-tim...
damage to the gears actuating the shuttle
bobbin case and shuttle laterally misaligned - hook passes too far from the needle sideways - the part keeping the hook is secured on its rod with 1-2 screws, loosen them and move the piece a little along the shaft
both the bobbin and the needle thread must be left hanging free (no tension)
presser foot must be lifted
handwheel is usually rotated by hand with top of the wheel coming towards you