spitting dust out

I have had my cordless sweeper several years and swear by it - so lightweight, hand and easy to use however lately it has taken to picking the fluff up then spitting it back out again. It has been cleaned inside and out - even taken to pieces and reassembled. I empty it after each use - emptying is so simple. There is no "blockage" than I can see - has anyone has this problem and if so, how can it be rectified, if indeed it can be rectifed. Perhaps I have just worn my sweeper out.