First things first, 

SUPER pleased about the increased performance of the select component. When I compare it to 5.2.6 it's now almost instantaneous. 

Also, the dropdown depending on how many items are after the filtering is now responsive. Very neat. The customer was pleased by this. 

I only seem to have a minor issue. When I use it anywhere else, it seems perfectly fine.

https://gyazo.com/1d3adb367657d9fe9bc521e14c51a840

When I put it in the header it seems to break. 

https://gyazo.com/16af5347afc1aaf1eac97ea48aef2b39

It always has a horizontal scroll bar. And the seperator between the filter and the options isn't centered and ends on the right side. 

I fixed it on my end for now, by applying to the dropdown-content "overflow-x:hidden" and on the form-control "margin-left: 0rem"

Somewhat unrelated to this, since the css classes have changed since version 5.2.6 due to the rewrite, what's the class to reduce the transition time of the animation?