Hello, I had the same problem and it got only partially fixed for me in 1.5.9.
Three of my buttons were affected. And after upgrade to 1.5.9 one has found its original place.
But two are still messing up as you can see here. Maybe because they are both inside a classic vue transition component ? Or maybe set as fixed-bottom ?

Here is before upgrade from 1.0.0 to 1.5.9

Here is after upgrade from 1.0.0 to 1.5.9

Here is code of the buttons.

Thanks for your help !:)