yeah had the thump for a a while , reset did nothing .
luckily im pretty experienced with electric motors so pulled mine apart and recond it(stripped motor completly and cleaned with motor cleaned ect etc)
in my case and probably your the brushes had clogged and wre not always springin into contact so the thump was just getting them free each time.
follow one of the guides and it should fix it , takes while but well worth the effort.