Window Pane Shattered - trying to discover cause

A curved window in our house shattered when we weren’t home so the cause is unknown. While we are waiting to get on the calendar for the manufacturer to make a replacement and the installer to install, I’ve noticed about a 3/4: gap in what I would call the “trim piece”, which looks like 3 pieces were used instead of one smooth piece like on all the other windows in the house. The window is Milgard Trinsic with Vinyl Window Frame. We have matching “mirror image” window where there is no gap in the trim. There are a couple houses in the neighborhood with the same window and all those trim pieces are singular.

My suspicion is that this gap may have prevented achieving a good seal between the panes and through repeated heating and cooling cycles (we get a lot of sun in this part of California) the seal failed, the cavity between panes became super heated and the exterior pane shattered.

House is 4 years old. We have contacted the builder and Milgard and are pursuing options there.

But I feel I need to resolve if this gap is a problem as the installer is proposing reusing the existing Frame and I wouldn’t want this to happen again.

Does anyone have any idea about such a thing? Or suggestions on other subs or places to ask?

TIA