The input boxes run a validation check whenever the user presses enter or focuses out of them; if this check determines the input value to be invalid, the stylesheet will shake.
In your case, you were probably typing some input before you clicked the hint box, thus focusing out of the input and invoking the validation check.
Okay, but this validation happens instead of opening the help dialog. Whatever event triggers there eats the button click.
When typing an incorrect input, the first place a user will go to fix it is the help. It's a bit of a catch-22 when the help button will only help you after you fix your typos.
In your case, you were probably typing some input before you clicked the hint box, thus focusing out of the input and invoking the validation check.