Unfortunately, there is a known bug affecting IX percentages applied to width or height where Webflow substituted pixels values in place of % or VW VH:
Sorry you are experiencing this too. It has been around for a while. I have seen a hack that may work for your situation by deliberately overshooting the target and enforcing a CSS max-width % to preempt the overshoot. The combo works effectively, but the tween ends abruptly for some width scenarios of course. I can search and try to point you in the right direction if you are interested. If you are working within a container instead of a full screen layout it should do the trick.