Re: Mine too!
yeah i had this too - when u accelerate the fluid tips back and sensor drops down (its on end of a float) mine was cos i was losing fluid - fast - thru a split caliper hose. check hoses, drum cylinders for seal wear, and keep an eye on fluid. top it up and if it drains again, you have a leak somewhere, get it sorted asap. as i found out no brakes is v.scary!!
Adam