Short description of your issue:

A4A dynamically replaced CLICK_X/CLICK_Y for any links within its friendly frame upon click for AMP creatives. However, it is possible that AMP creatives can be cross domained if they could not be verified client-side (or failed server-side validation). Need to ensure that CLICK_X/CLICK_Y occurs in this situation.

Original design placed CLICK_X/CLICK_Y replacement on document for all AMP documents but was moved into amp-a4a.js by @cramforce We need it to exist in the cross domained AMP creative case as well (likely as part of amp-inabox effort).