Aoycocr U3S/HYS-U1S-SOCKET-V1.3 not appearing with intermediate firmware

I have issues getting a device to flash.

These are Aoycocr U3S/HYS-U1S-SOCKET-V1.3, bought in a four pack.
I have one of these apart, inside the PCB is labelled 2018-09-21 and the model above.

I have also purchased two of these as single plugs and tuya-convert worked fine for those. I'm using a Pi4 and had no problems with them. I have noticed the text on the back of the four-pack of plugs is slightly larger, so I believe these are slightly different.

I've checked the new PSK issue, but my ID seems to start 01 not 02.

```
new client on port 443 from 10.42.42.23:29247
ID: 0142416f68626d643661473931494652310146c3b21f9a2c0e35f33f3fd7a0f9715fb9817857afd0b9911455c27b30ec93e2
PSK: e65039ba52dca3487b19ba80595c5ef3ff17d7b52a022eff2fd619612d8aefe1
```

I've tried this a few times, including with another device connected to mobile first or not.
It seems that once the device (flashing) has been sent the first stage, it reboots and goes back to normal (light on).

Happy to do firmware dumps/flashing/tcpdump if someone can point me in the right direction of what to try next. This doesn't seem to be the same issue as #727 which is why I'm opening it here.

Files attached;
[smarthack-wifi.log](https://github.com/ct-Open-Source/tuya-convert/files/5091831/smarthack-wifi.log)
[smarthack-web.log](https://github.com/ct-Open-Source/tuya-convert/files/5091832/smarthack-web.log)
[smarthack-udp.log](https://github.com/ct-Open-Source/tuya-convert/files/5091833/smarthack-udp.log)
[smarthack-psk.log](https://github.com/ct-Open-Source/tuya-convert/files/5091834/smarthack-psk.log)
[smarthack-mqtt.log](https://github.com/ct-Open-Source/tuya-convert/files/5091835/smarthack-mqtt.log)

Start by reading the attached smarthack-wifi.log, smarthack-web.log, smarthack-udp.log, smarthack-psk.log, and smarthack-mqtt.log, then compare the failure with issue #727. Reproduce the first-stage flash attempt on the Raspberry Pi 4 and identify where the device returns to normal operation. Done means the cause is documented with reproducible evidence or an actionable fix is identified.

Written by the indexing model from the issue text.