Changing the Magnification parameter (lower left corner of active notebook window: 100%) accidentally happens by zooming the screen resolution via tapping the touchpad with two fingers. Try the two finger stretch and observe the the lower left of the active notebook window.

There are two ways to avoid ; Tap very careful
or switch two finger zooming Off in the windows system setting

The second method nearly makes it impossible to write and read text in browser interfaces like this one or in stackexchange.

There exist laptops, that are even sensitive to two finger zoom by touching the case somewhere in the vincinity of the touchpad : the touchpad is a device sensitive to static electricity. Internally the touchpad area is Faraday - shielded by a grounded metallic enclosure.