Hook comes down and gets stuck on the Presser foot
The wiper or Upper thread Hook comes down and gets stuck on the Presser foot.
You need to make sure that the Upper Thread Hook is not bent . If it's OK then take a look at the thread holder (the bracket behind the needles with Velcro attached ).
The upper thread hook has to move freely inside the Velcro . If it's getting hung up on the presser foot that means it's probably not popping back up soon enough , and that could be because the thread holder is not adjusted correctly.
It can get out of line from banging against something like a hoop.
Loosen the 2 screws on either side that attach the entire assembly to the sewing head and with the upper thread hook in the stuck down position, try adjusting the bracket until the UTH pops back up and moves up and down freely.
There are also 2 pivot screws on either side of the bracket that allow the bracket to be tilted. So you have 2 adjustments, up and down and back and forth.
Once adjusted correctly the UTH should glide easily in and out of the Velcro.
If that does not fix it you could have an upper thread hook solenoid going out or a power supply issue.