Mine does it all the time after they been fed and cleaned out they push themselfs through the new sawdust i put in, its like they trying to rub their scent in the clean sawdust
Old trick i used to use on ticks in akward places that cant be removed easy is get your missis nail varnish and cover the white sack with it, it dries in a couple of minutes and stops them breathing and they drop off ( you can use any colour )