hi,as far as i can i know they dont often fail as i have owned two IS 200's and has never been an issue,try giving the casing a few gentle taps/knocks and spray again with WD 40 and see what happens.
I tried again earlier today and it seems a bit better, at one point it stopped working altogether after i was opening and closing it a few times. Going to leave it and try again tomorrow, must have used half a can of WD40 already...... there was a fair amount of filth and dirt coming out when i sprayed it in. ......that sounds disgusting sorry.