The film in a normal load passes over an end roller. That roller detects the film and meters the frames as it counts.
If the film is not making good contact with this roller or there is an adjsutment out of spec dealing with this roller... it will wind on forever nonstop.. as well as some other intermittant inconsistancies... like you say it has a symptom with the dark slide.
As also mentioned by others.. there is a small tab that gets pushed in when the door is closed, that engages the counting mechanism and roller sytem. If the tab is not properly pushed in or the mechanism is out of spec it too will give you similar symptoms... but still part of trhe same roller mechanism linked by a signal arm; that is the most comon part to go out of adjustment..
But it all starts as you described above.. all weird quirky symptoms... asking for service.. not screaming yet. Perhaps the service costs too much these days... so buy a backup for $25 before this one drops dead on you.. cheaper solution?