Mouse input is totally broken

As the title says - mouse input is broken and creates a stuttery mess, which has basically stopped me from playing. There are other posts about this but there is no resolution and nothing can be fixed on the user side. 

170fps feels like 42fps - enabling framegen sort of smooths it out, but not completely. 

Controller input is totally smooth. 

If you haven't read the other much larger threads on this issue, don't bother commenting with possible fixes on the user side - everything has been tried and nothing we can do will fix it.