What causes bubbles on my iPhone 16e screen guard?

I purchased a new iPhone 16e a few months ago and since then have needed to replace 3 Belkin screen guards due to product fail.

usually the problem appears after a few weeks with a small bubble appearing either at the top or bottom of the iPhone screeen. Overtime the bubble spreads across the upper or lower part of the screen.

Belkin have so far replaced the screen guards and I have always had Apple do the fitting.

Neither I or my local Apple Store know why this problem is occurring.

This problem never happened with my earlier IPhone XR.

[Re-Titled by Moderator]

Original Title: iPhone 16e screen guard problems