Bulb stuck with intermediate firmware

I have a pair of generic wifi light bulbs that look just like [this one](https://www.gearbest.com/smart-bulbs/pp_009302531844.html). No identifying markings on the outside, but I did open one up and confirm it's using an Espressif board.

I put the bulb in flash mode and ran `./start_flash.sh`. After a couple tries, I get a long set of dots after a `Resending SmartConfig packets`, then it just stops and I get the `Device did not appear with the intermediate firmware` message.

When I powercycle the bulb, no `vtrust-recovery` network is visible, however when I have the `vtrust-flash` network up the bulb flickers every ~10 seconds. Tailing `smarthack-wifi.log` shows those flickers are related to immediate connect/disconnect events from the bulb. This makes me believe that it's running the intermediate firmware. I am unable to curl 10.42.42.42 during this time, likely because the bulb doesn't stay connected for more than a fraction of a second.

Any ideas on how to keep the bulb connected to the wifi long enough to upload the new firmware?

```
pi@raspberrypi:~/tuya-convert $ ./start_flash.sh
tuya-convert v2.4.3
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.
sudo: ufw: command not found
======================================================
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
........................................................................................
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]

======================================================
Cleaning up...
Closing AP
Exiting...
```

[smarthack-psk.log](https://github.com/ct-Open-Source/tuya-convert/files/4632690/smarthack-psk.log)
[smarthack-udp.log](https://github.com/ct-Open-Source/tuya-convert/files/4632691/smarthack-udp.log)
[smarthack-web.log](https://github.com/ct-Open-Source/tuya-convert/files/4632692/smarthack-web.log)
[smarthack-wifi.log](https://github.com/ct-Open-Source/tuya-convert/files/4632693/smarthack-wifi.log)
[smarthack-mqtt.log](https://github.com/ct-Open-Source/tuya-convert/files/4632694/smarthack-mqtt.log)

Start by reproducing the failure with ./start_flash.sh and inspect the linked smarthack-psk.log, smarthack-udp.log, smarthack-web.log, smarthack-wifi.log, and smarthack-mqtt.log files. Trace the intermediate-firmware detection and the bulb's connect/disconnect events, then document a reproducible cause or verified way to complete the upload.

Written by the indexing model from the issue text.