pressure washer, patio attatchment.

Hi , Karcher k4 pressure washer, The patio accessory T250 t racer patio cleaner wasworking like a dream. Had a cuppa and went to start it again and all i get is a pulsing as if there is a kink in the hose or no water ~ all works fine with the lances. I dismantled the spinner bar and found some grud round the nozzle area ~ cleaned it all but still no go ~ it wont spin, but free to spin with my hand..
Anything else I can try before I go get new Nozzles , O rings etc ?
I wondered if the O rings maybe gone but have only used the attachement about 7 hrs ~
cheers in case anybody knows >>
t/c John

I have the alto one similar I guess it does play up at times, assuming water is jetting out of the holes I find holding it up (pointing away) and giving the arm a spin often clears it.