Toggle between modals makes the backdrop too dark

[tkrotoff]

Prerequisites

• [X] I have searched for duplicate or closed issues
• [X] I have validated any HTML to avoid common problems
• [X] I have read the contributing guidelines

Describe the issue

Toggle between modals makes the backdrop too dark during a short time because there are 2 div modal-backdrop with opacity 0.5 which adds up and becomes opacity 1.0.

https://user-images.githubusercontent.com/643434/159191366-f4afb8e6-370d-4e4d-be01-78132cf64d6c.mov

Can be verified with 5.1.3 and also using main.

Reduced test cases

https://getbootstrap.com/docs/5.1/components/modal/#toggle-between-modals

Can be best seen by slowing down the animation:

.fade {
  transition: opacity 1s linear; // instead of 0.15s
}

What operating system(s) are you seeing the problem on?

macOS

What version of Bootstrap are you using?

v5.1.3 and main

[tkrotoff]

I don't think this is worth fixing

[oakleaf]

How is this not worth fixing? I believe 200% it is, it looks like a glitch. I propose that if a backdrop already exists, do not populate a new one, re-use the old already existing one instead.

Or are there any solution to this yet?