Classic fault on the 950’s, it will be the carbon brush. Run the lift off slightly at the top to expose brush and clean contact area with a bit of emery cloth and it will be fine . I replace every one from the factory with longer brushes with a stronger spring.
You can take the brush out in situ if you wish but getting it back in is very tricky. You do not need to take the lift off fully, just enough and you see the brush pop out. Push it back flush with your finger and go very steady when driving it back on, no drama
