Aqualisa quarts digital shower blue control indicators?

I have problems turning the boost off and sometimes turning it on. The control panel has now been changed three times but the same problem returns after a short period. What I have noticed now is that the boost blue indicator appears to be dimly lit all the time while the boost is not in use. Occasionally the shower will go into boost when not switched to boost. The dimly lit indicator has been present on the last two control units. The control units have been replaced by me each time but have been supplied by Aqualisa under warrantee. I have reported the dimly lit indicator each time but their telephone man is unable to say if this is indicative of a fault apart from the control panel. Thanks for any help