Mira Sports max low flow problem?

I have a 10.8Kw Mira sports max shower, which has a low flow fault. The water flowing through the shower seams to be fine, I have cleaned the filter inside and after this it worked fine but it has now stopped after only 2 days. I have taken the head off and the shower will work in low mode but not it any of the others.

Has anyone any ideas what the fault may be.