Howie,
Some basic double jump functionality was added to the engine in 4.13 (which is why the Jump Max Count variable was introduced). The behavior you’re describing is as intended for the built in double jumping.
In order to get around this behavior, you can modify the CanJumpInternal_Implementation and CheckJumpInput function in ACharacter (note, these are both C++ functions not exposed to blueprints).
Thanks,
Jon N.