Exactly as I would have thought. Everything required - yes, everything you mentioned and more - was in place, and I was totally confident of receiving the extension. But the door was slammed in my face just because of the place of issue of the visa. I am now permitted to stay until 3 April 2020.
Yes, I had the receipt in my passport when I applied, and it was already 2 months since I had registered. All my paperwork had been accepted, until someone higher up noticed that my visa was from another province, and then I was rejected.
I am very anxious to find a way to stop this happening again next time I apply
No, I registered my address before applying for the extension. They still refused, and sent me back to Nonthaburi, where I was also initially refused because I had moved out of the province.