The .vw-search-button.button--cta rule was added to fix issues that occur on many custom styles that have increased the size of .button--cta elements, so that the button still fits in the input-group. However, it looks like more recent versions of XenForo 2.1 don't need the line-height part of the rule anymore, since .button is now a flex element. So in the next release, line-height will only be included for XenForo 2.0 (not 2.1).
Fixed the missing Caption label in the next release.