I use multiple screens, but this also happened on a single screen setup. When I pass my Logitech M705 wireless mouse over the composition panel when moving from one panel to another, automatically zooms in to the highest number if I move to the left and zooms out to the smallest percentage if I'm moving right. I am not touching the scrolling wheel or buttons -- I've been very cognizant of the possibility of a spurious mouse command.
If I pass the mouse below or above the composition panel, it does not zoom, only if the mouse pointer moves across the panel.
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