To add to this, using 100vw is a common mistake - the width of the viewport takes into consideration your whole window real estate. Including the scrollbar. Therefore an element of a 100vw will take the whole width of the window even if the scrollbar makes this window technically narrower. Using 100% will take the scroll element into consideration when determining the available width.
Yea i had this problem myself so i just asked my wife(she is a coder) to explained it to me was bugging me for a long time. And had to fix this a few times but actually, didnt know what i was doing wrong so yay now i finally get it.
But what kind of feature of site would you need the vw for? instead of the 100%?
@argogiant You just put an end to a full evening of troubleshooting - crazy how it all comes down to 2 letters!! Similarly, I had a Grid block with 100vw causing the bug > changed to 100% > Done & done.