The way the regulators work is a little like a garage door, a spring balance. So even though the window will stay in any position while the vehicle is stopped, I have a feeling when driving it will creep open or closed depending on what position its closest to.
With the correct window felt it may have had enough friction to stay when new, but the felt I used is loose and let’s the glass float in the track so that could be part of the issue.
There’s no service information about this type of window regulator that I can find, so there’s some guessing going on
