Wotto , I suggest you take the mechanism apart , remove the cam from the little pivot that is also held to the playfield with 4 screws , now see if the pin that is pressed onto the pivot bracket is tight , if it is moving at all this will cause the problem you are having.
What happens is the mechanism will move freely with your hand but when the coil is activated that pin moves to one side binding up the cam , have seen this countless times.
BTW , the coil will not fire if it was Zero ohms , the Transistor can not sink this amount of current it will blow straight away , the same will happen if the diode is shorted , in either case the coil would never fire at all because the fuse would be blown the moment this happened.
There are other 26/1200 coils in the machine , if you want to confirm the coil just borrow one from another spot and test again.
