I did a job for a friend of mine replacing a couple of storm windows with replacement windows. He tells me the other day that one night he hears a pop and looks at one of the windows and it has a crack in the pane. Temp was November in NJ not freezing cold. I plumbed windows and didn’t overtighten screws for window insides.  I don’t get it nothing was out of level or bowed. This is a first for me.

PS I didn’t measure them he did

Any thoughts? similar incidents.

thanks