P2A00 woes. O2 sensor... again

[takjak2]

At ~19k miles my car threw this code, reset it multiple times, and had the O2 sensor, as specified in in service manual, replaced under warranty. No more SES light for almost 3k miles.

After some rough driving it came again and I took it to a different dealership. They again replaced an O2 sensor under warranty, noting that the wire had "been stripped"/abraded some (that could have been me) and that it looked jarred (sounded to me like a poor install the last time?). Supervisor said that should fix it but "if it comes up again we'll have to look at the fuel system" [implied sender]. Another thousand plus miles no SES light.

There was a P0400 code (I think that's what it was), same as others with aftermarket exhausts or test pipes except that mine is entirely stock nismo. Reset it, saw it again after a hundred miles, reset it, and have not seen it for at least another 1000 miles.

Now the P2A00 is back again and haunting me after a reset. Any thoughts before it goes in tomorrow?