It is my understanding, and has been for the past 40 years, any waving signal by any "R" player during a scrimmage kick causes the ball to become dead upon possession by "R". Some of the officials in my area don"t agree with that statement and say if the signal is below the shoulders to let it go. No where in the rule book does it indicate there is a difference between a signal above the shoulders and a signal below.
Let me add a couple of comments: I am not referring to a valid signal as we all know the definition of a valid fair catch signal. The rule is very clear, in my opinion, that any signal, valid or invalid , causes the ball to be come dead upon possession. No where do the rules leave it up to the judgement of the official to determine the "keep away signal" is different or should not be defined as an invalid signal. The only exception I am aware of is if the "R" player is trying to shield his eyes from the sun.