Aoycocr U3S plugs not flashing

I bought 2 four packs of these from Amazon last week (UK).
Six of the eight devices have worked perfectly, two will not respond to their button when powered on, can't get into fast flash mode.

I have tried rerunning install_prereq.sh and running again (on a pi4)
[smarthack-mqtt.log](https://github.com/ct-Open-Source/tuya-convert/files/5012427/smarthack-mqtt.log)
[smarthack-psk.log](https://github.com/ct-Open-Source/tuya-convert/files/5012428/smarthack-psk.log)
[smarthack-udp.log](https://github.com/ct-Open-Source/tuya-convert/files/5012429/smarthack-udp.log)
[smarthack-web.log](https://github.com/ct-Open-Source/tuya-convert/files/5012430/smarthack-web.log)
[smarthack-wifi.log](https://github.com/ct-Open-Source/tuya-convert/files/5012431/smarthack-wifi.log)

Shell output below but I notice at retry five, my other machine can no longer ping the pi.

```
pi@raspberrypi:~/tuya-convert $ ./install_prereq.sh
Hit:1 http://archive.raspberrypi.org/debian buster InRelease
Hit:2 http://raspbian.raspberrypi.org/raspbian buster InRelease
Reading package lists... Done
Reading package lists... Done
Building dependency tree
Reading state information... Done
build-essential is already the newest version (12.6).
curl is already the newest version (7.64.0-4+deb10u1).
git is already the newest version (1:2.20.1-2+deb10u3).
haveged is already the newest version (1.9.1-7).
hostapd is already the newest version (2:2.7+git20190128+0c1e29f-6+deb10u2).
iw is already the newest version (5.0.1-1).
mosquitto is already the newest version (1.5.7-1+deb10u1).
net-tools is already the newest version (1.60+git20180626.aebd88e-1).
python3-dev is already the newest version (3.7.3-1).
python3-setuptools is already the newest version (40.8.0-1).
python3-wheel is already the newest version (0.32.3-2).
screen is already the newest version (4.6.2-3).
dnsmasq is already the newest version (2.80-1+rpt1).
libssl-dev is already the newest version (1.1.1d-0+deb10u3+rpt1).
python3-pip is already the newest version (18.1-5+rpt1).
0 upgraded, 0 newly installed, 0 to remove and 90 not upgraded.
Looking in indexes: https://pypi.org/simple, https://www.piwheels.org/simple
Collecting git+https://github.com/drbild/sslpsk.git
Cloning https://github.com/drbild/sslpsk.git to /tmp/pip-req-build-datrju8g
Requirement already up-to-date: paho-mqtt in /usr/local/lib/python3.7/dist-packages (1.5.0)
Requirement already up-to-date: tornado in /usr/local/lib/python3.7/dist-packages (6.0.4)
Requirement already up-to-date: pycryptodomex in /usr/local/lib/python3.7/dist-packages (3.9.8)
Building wheels for collected packages: sslpsk
Running setup.py bdist_wheel for sslpsk ... done
Stored in directory: /tmp/pip-ephem-wheel-cache-nhwdtcyy/wheels/19/5d/ca/bb92c9b2e4aa13e12306893a6eadd16dbfcdfca942476ecfa1
Successfully built sslpsk
Installing collected packages: sslpsk
Found existing installation: sslpsk 1.0.0
Uninstalling sslpsk-1.0.0:
Successfully uninstalled sslpsk-1.0.0
Successfully installed sslpsk-1.0.0
Ready to start upgrade
pi@raspberrypi:~/tuya-convert $ ./start_flash.sh
tuya-convert v2.4.4
Checking for network interface wlan0... Found.
Checking UDP port 53... Available.
Checking UDP port 67... Available.
Checking TCP port 80... Available.
Checking TCP port 443... Available.
Checking UDP port 6666... Available.
Checking UDP port 6667... Available.
Checking TCP port 1883... Available.
Checking TCP port 8886... Available.
======================================================
Starting AP in a screen
Starting web server in a screen
Starting Mosquitto in a screen
Starting PSK frontend in a screen
Starting Tuya Discovery in a screen

======================================================

IMPORTANT
1. Connect any other device (a smartphone or something) to the WIFI vtrust-flash
This step is IMPORTANT otherwise the smartconfig may not work!
2. Put your IoT device in autoconfig/smartconfig/pairing mode (LED will blink fast). This is usually done by pressing and holding the primary button of the device
Make sure nothing else is plugged into your IoT device while attempting to flash.
3. Press ENTER to continue

======================================================
Starting smart config pairing procedure
Waiting for the device to install the intermediate firmware
Put device in EZ config mode (blinking fast)
Sending SSID vtrust-flash
Sending wifiPassword
Sending token 00000000
Sending secret 0101
................
SmartConfig complete.
Resending SmartConfig Packets
.................
SmartConfig complete.
Resending SmartConfig Packets
.................
SmartConfig complete.
Resending SmartConfig Packets
................
SmartConfig complete.
Resending SmartConfig Packets
.................
SmartConfig complete.
Resending SmartConfig Packets
.................
SmartConfig complete.
Resending SmartConfig Packets
................
SmartConfig complete.
Resending SmartConfig Packets
.................
SmartConfig complete.
Resending SmartConfig Packets
.................
SmartConfig complete.
Resending SmartConfig Packets
................
SmartConfig complete.
Resending SmartConfig Packets
..............
Device did not appear with the intermediate firmware
Check the *.log files in the scripts folder
Do you want to try flashing another device? [y/N] n
======================================================
Cleaning up...
Closing AP
Exiting...
pi@raspberrypi:~/tuya-convert $`

```

Logs uploaded.