Boulder, CO
This also happens when the plunger gets mushroomed at the tip...and then it drags and catches inside of the coil (sleeve) when trying to return to a resting position.
Take the coil stop off. Inspect the coil stop. Slide the coil off. Look at the coil sleeve. Look at the plunger. If stuff is beat up, flattened, or has sharp edges, replace them. For me, a flipper rebuild is: new coil sleeve, new plunger & link, new coil stop.
Also, as mentioned, the part of your coil where the red wire is attached has snapped off and is going to need to be replaced eventually. You can just get a new coil. Replacing it involves soldering those two wires. Even if you haven't done it before, it's not something you need to be afraid of. 
