I think last I heard the location of the OHL that is causing the issues was originally thought to be in the Newark areas on the down line as it only the pantographs at the first class end of Azuma sets and the pointed cab end, think it's the no1 end, carbon that is showing damage this happened a few months back but there seemed to be a greater priority in finding the issue, with train pantographs examined at each stop and I think it was ultimately traced to a dropper hanging below the contact wore that was the cause.
It has also been mentioned that there was a nance it could be on the Airedale lines but then, as already mentioned, the northern emus would be even worse hit as they pass numerous times through the area each day so the damage would be worse.