The original nozzle trigger/piston mechanism on my Hoover CleanSlate stopped spraying properly and would only drip. Grease was not a real fix, and in my case it was not needed at all. The real problem seems to be the original rings: for some reason, they do not slide well against the surface and tend to bind up, so the button stops moving properly in either direction.

I designed simple replacement rings and printed them in TPU 95A. Unlike the original rounded rings, these have a flat profile, and they work much better. After installing them, the trigger moves smoothly and consistently, like it should — up, down, up, down, just like a proper trigger. It now sprays normally again.

I personally use the 11.4 mm version, but I also attached an 11.6 mm version just in case.