Scrollbar is overlapped in component selector

[froschdesign]

In Firefox 62:

@thexpand
Can you look at this? Thanks!

[thexpand]

@froschdesign Yes, of course. I'll reply as soon as I find the reason for this and apply a fix as a PR.
You can assign me.

UPDATE (2018-10-25): I'm not sure if this problem has a solution.
I provide some reading material at the bottom, but I'll summarize the main problem. Because we're using a fixed positioned <div>, it's being pushed away from its container's layout, causing it to go over the scroll bar. I've thought of making the element's position absolute, but that way we'll have to update its top or translate: transformY() properties as scrolling happens. Unfortunately, the latter two will result in bad performance, as the sticky element will jump a little bit (won't go smoothly).
https://stackoverflow.com/questions/23057961/fixed-div-overlaps-scrollbar