How to prevent edges of adjoining windows from adhering to each other ?

[Sebastian42]

I have turned Win10's SNAP off - and so the feature of touching edges moving-as-one, should not apply - yet it does. When I move the adjoining edge of one window, that of the other moves with it - I do NOT want that to happen. How can I prevent that ?
It turns out that it is a phenomenon that comes and goes, and comes back.