I've tried to find this issue looking for +modal +scroll but have failed to find it, hence creating it.

Everytime a modal dialog is shown, the "disabled" body hides any existing scroll bar and, as a result, the whole body is "moved/offset" by some points.

It's a small, but very annoying issue to get the whole page "vibrating" that way. Would be great to keep body quiet when modals (and we are using them more and more) are used.

I can reproduce it consistently under both Safari and Chrome with scroll bars enabled.

Maybe related, I've found this, just in case it helps:

https://github.com/twbs/bootstrap/issues/9855

Ciao