I am trying to re-create this bug, but I want to at least get the conversation started.
When I modify certain formulas in Buttons, the button will be shown as not usable due to a missing closed parenthesis. I will check the formula and see that no closed parenthesis is actually needed. And if I do add one, it will throw an error. The only way to rectify the issue is to cut the entire formula, then re-open the button and paste the formula back in. Then the exact same formula will work.