Help flashing ESP8266 based switch w/ USB to Serial CH340

Some of you may remember my thread here from a few months ago. So I managed to get myself a Deta 2-gang Swich plus a USB to Serial CH340 programmer.

Using Tasmotizer 1.2 I was able to get one of the Deta 2-gang Switches programmed with the generic firmware and added to HomeAssistant over MQTT - everything works great.

However I now have another 2-gang and 1-gang (verified these work according to this tutorial here) however I am having a lot of trouble getting these two new switches flashed or “Tasmotized”.

No matter what I do, I am getting the ol “Failed to connect to ESP8266: Timed out waiting for packet header” error.

Things I’ve checked so far:

  • Double checked all the jumpers to make sure everything is good (and I haven’t done anything silly like cross RX/TX) - I have wires in the same position as I had when I flashed my 1st 2-gang switch.
  • Ensured correct voltage (the CH340 is a switchable 5/3.3V - I verified I am getting 3.25V out of the board).

Any ideas?

EDIT Just as I finished making this post, I decided to swap RX and TX around and it works. This is very odd as I could have sworn the first 2-gang switch I did had the RX and TX the right way around between the programmer & the wiring shown in the guide linked above.