Hi there,
your CSS only works if the label immediately follows the input element (CSS "+" selector). Now if for any reason other HTML-elements are inbetween, it doesn't work anymore.
Example: https://parsleyjs.org/ (used f.e. in Powermail extension for TYPO3) places a <ul> after the input element if errors occur, so it is then between input and label.
Solution: Use "~" instead of "+" as selector for labels. It should not break anything (atleast I think so).
Any chance of a change on this for BS v4 + v5?
Greets