Mine have developed an issue where I turn it on to the lowest speed, and it goes intermittent like the OP said. It doesn't change speed no matter which setting I put it to, and if i shut if off it randomly does it like 4-7 cycles later.
Going to run a better search and investigate, i'm sure someone else has had the same problem.
EDIT: This is somewhat familiar.....I'll probably just end up buying the motor and everything from a parts car and it should go away lol.