Steps to reproduce the issue

1. Go to administrator/index.php?option=com_templates
2. Reduce viewport width so that the toolbar is controlled via a dropdown (see screenshot)
3. Toggle the button to expand the toolbar buttons

Expected result

Smooth animation

Actual result

Glitchy animation

At the beginning and end of the animation, I believe it detects any additional margins/paddings and then has to recalculate the height, which causes the animation to become glitchy.