I don't have much experience with eTap (Di2 guy), but isn't there a function button on the RD that allows you shift inboard or outboard with a single or double-click? When the RD is acting up, are you still able to shift using the function button on the RD? If so, it may be a pairing issue with your shifter, and the RD is fine. If you can't shift with the function button, then the problem is narrowed down to something inside the RD (like a sketchy servo).