[Update] I had rebuild the issue below:
https://sp0033212000.github.io/fixedProblem/
I had a site.
I was work well except open it by target _blank.
When I into the site directly, it normal enter image description here
but when I into it by new tab, the bottom button was be covered. enter image description here
I guest it was viewport issue but no idea how to fix it.
could some one give me suggest how to handle this problem?