Did you have first tab set to open by default?
My guess is that since the tab isn’t open when the quote slider code processes that it doesn’t leave enough room for it and the overflow is hidden.
Have a look at Doobox’ answer to this thread towards the bottom of the page - I think you’ll find it won’t work because the slider content is hidden when the page loads. (He’s referring to his onw stack but the principle is the same, I think).
This is true for all slider type stacks on page load no matter what the theme is. That is why it is not a good idea to use a slider stack in tabs or lightboxes. The starting height gets set to 0 and it looks like they do not load, but you just can’t see them. A good rule to remember is if it is a slider, it needs to be seen on page load for it to work correctly. (can’t tell I get this question a lot in support can you??)