you have multiple instances of the Server Validation behavior on the page, there should only be 1. There should be one server valdation server behavior with all of the validation types defined in that one behavior
The validation show if for the required checbox is for one of the other 2 server validation server behaviors.
i would suggest removing the validation show if behaviors and the other 2 instances of the server validation behavior, leave only the first one, then recreate the validation show if behaviors.