When they added clojure.spec. It started validating macros at compile time. If you were previously using an illegal syntax, but that somehow didn't cause any issues, those would now throw a compile time error.

Overall it was for the best, since prior to that it was just weird code that had a bit of a undefined behavior since it wasn't using the macro in the proper way. But it still meant we had to go and fix a few of them so they compiled again. Though in the process we realized that we were misusing the macros to begin with.