buttons should never move. ever. the number of times I have hit the wrong button because in the time it took for my finger to reach the screen some new data loaded off the network and reflowed the layout of the page such that a different, wrong button was now under my finger and gets hit instead is... not small.
especially true on mobile. maaaybe on desktop you can check to see if my mouse is hovering over a button before moving it, but generally don't move the fucking buttons