Webapp bottom tabbar shrinks down when reloading on Safari iOS

Hi, I've been scratching my head for few days for the same problem I'm having.

When I initially tab into my web-app, the bottom tab bar renders beautifully, with the bottom 0px and height of 64px.

But the issue occurs when I leave the app and re-enter after few seconds, suddenly the tab bar container gets shrink down from where I expected to be leaving a horror gray area.

On Android shows no problem but with iPhone-which I think is because of Safari iOS bottom navigator-the bottom: 0px, doesn't get the right layout.

I'm attaching pictures to describe what I'm going through.

There's one more weird part. I have several other apps which basically has same code line, front-end and back-end, but only two of them seem to show the same bug.

Is this something to do with the native? Would appreciate any suggestions! Thank you,

Webapp bottom tabbar shrinks down when reloading on Safari iOS
 
 
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