Canon P Frame Counter Reset Question

Perhaps this is a silly question, but should the frame counter reset when the back is opened? The English-language manual says only "when a new film is inserted". I last used the camera about a month ago and it was fine, today I noticed that counter is stuck around 24 even though I opened the back (and also did so when I last removed film, too).

On the Canon P there is a plunger in the top slot for the rear door light trap between the sprocket reel and the take-up spool. When the door is closed, this plunger is depressed, permitting the film counter to advance. When the door is opened, the plunger is free to extend into the slot, which permits the frame counter to reset to "S". If the frame counter does not reset, something may be gummed up or broken in the film counter mechanism.