A Samsung Android 4.1.2 update oddity

The Mrs' Samsung Note 2 had an update from Android 4.1.1 to 4.1.2 delivered the other day. And all hell broke loose.

Wifi stopped working. The Mrs was not amused.

After a lot of faffing around, and debating whether to flash the phone back to 4.1.1 using Odin, I stumbled across a rather strange pattern with this particular problem - it was only hot spots that the phone had been used on previously that had stopped working ...

Renaming our home WiFi hotspot got it working again, but I have to question what is getting stored, even without adding her Google or Samsung accounts back onto the phone after flashing it and a factory reset ...  seems something is lurking somewhere ...