I'd like to offer a suggestion about the thread jumping out of the slot.
Notice that the "slot" is actually a hole with a wedge leading into it? Notice as well that the wedge cutout does NOT go to the edges of the hole? I am pretty sure that this is not by accident. It would have actually been easier for them to make it a smooth round bottomed wedge shape if they wanted to.
Seeing this I did a few tests last night and it appears that as long as the spool is NOT IN LINE with the "slot" but set to the side, those little wings catch the thread and keep it from hopping out. when I set the spool in line it hops out from time to time (mostly during deceleration)
your mileage may vary...