Thank you. Submitted the email.

Network section of M122

• WiFi -
  Network state is active
  WiFi module is connected to access point
  Failed messages: pending 0, notready 0, noresp 0
  WiFi firmware version 1.26
  WiFi MAC address f0:08:d1:03:81:1b
  WiFi Vcc 3.36, reset reason Power up
  WiFi flash size 2097152, free heap 23576
  WiFi IP address 192.168.0.30
  WiFi signal strength -35dBm, mode 802.11n, reconnections 0, sleep mode modem
  Clock register 00002002
  Socket states: 0 0 0 0 0 0 0 0

I've tried with incognito and Firefox in safe-mode, no change, it still won't upload.
The firmware for the wifi module has been reflashed each time I made firmware change:
When flashed with the latest release
Reflashed again with latest
Downloaded and reflashed with 3.4.0
Reflashed again with latest
Downloaded again this morning and reflashed with latest

Still won't upload.

When I put the unit in AP mode, it finally will accept an upload, but it is extremely slow (8-12Kb/sec).

The wifi works fine for control, other than not being able to upload to the unit. At this point, I'd be happy if I could swap it for a wired unit instead of wifi.

So far, I have tried:
Multiple reboots
Multiple SD cards
Multiple browsers
Multiple Access Points
Multiple computers (Linux and Windows)
Downloaded and loaded version 3.4.0 firmware, via Fallback procedure #1
Redownloaded and loaded version 3.4.1 firmware, via Fallback procedure #1

I am still unable to upload ANY files via DWC. I am able to print if I pull the SD card from the PanelDue and load the gcode files there. Wifi works, I am just unable to upload files.

What is the procedure for starting a warranty return on the Mini 5 board?
Unit was purchased this week from the Filistruder store in the US.

@phaedrux

I've tried with two different SD cards, with the card in the board and in the PanelDue.
I've tried with Firefox and Chromium both on Linux, and Firefox on Windows.
I purchased the board online from Filastruder on June 20, 2022. It arrived on Tuesday and I installed it yesterday.

@phaedrux

All I see is
Content Security Policy: Ignoring “'unsafe-inline'” within script-src: ‘strict-dynamic’ specified
Content Security Policy: Ignoring “https:” within script-src: ‘strict-dynamic’ specified
Content Security Policy: Ignoring “http:” within script-src: ‘strict-dynamic’ specified

Repeated until the upload fails.

Apparently the copy/paste cut off

• WiFi -
  Network state is active
  WiFi module is connected to access point
  Failed messages: pending 0, notready 0, noresp 0
  WiFi firmware version 1.26
  WiFi MAC address f0:08:d1:03:81:1b
  WiFi Vcc 3.36, reset reason Power up
  WiFi flash size 2097152, free heap 24424
  WiFi IP address 192.168.0.30
  WiFi signal strength -36dBm, mode 802.11n, reconnections 0, sleep mode modem
  Clock register 00002002
  Socket states: 0 0 0 0 0 0 0 0

@droftarts
Duet Web Control 3.4.1
Board: Duet 3 Mini 5+ (Mini5plus)
Firmware: RepRapFirmware for Duet 3 Mini 5+ 3.4.1 (2022-06-01)
Duet WiFi Server Version: 1.26

I attempted to upload the 3.4.1 zip package again, and same result. I've even moved the unit to use a different access point, and I've tried from a different computer.

@phaedrux
That failed too. I had to do the fallback plan of loading the files to the SD card.

The board came with an RC release older than 3.4.1 and I couldn't upload the zip to the board then, either.

Like I said, I can't upload anything through the DWC interface. The printer is printing fine, as long as I load the gcode files onto the SD card and plug it into the PanelDue.

@mac

TL;DR

In the web interface, click on Console on the left.
Just below the grey boxes at the top, labeled Status, Tools, and Temperature Chart, there is a blank space with a blue box to the right that says "Send"
In that box, you will need to enter:
M303 H0 S60
and click Send. This will run the PID tuning cycle. It may take up to an hour.

Once it finishes, you will see an output below it with an M307 line in it, something like:
M307 H0 R0.579 K0.295:0.000 D2.99 E1.35 S1.00 B0
Copy from M307 to the B0 at the end.
On the left, click on System, then click on config.g. This will open the config file for the printer in an editor.
Find the line in the "Heaters" section that starts with M307. Replace that line with the line you copied.
Click Save at the upper right, and it will ask if you want to reload the motherboard or run the config. Either will work to apply the change.

Background info:
PID stands for proportional–integral–derivative. It's a control loop that takes into account (in this case) how fast the print bed heats up and cools down, so it can modulate the heating to keep it stable, rather than the 'bang-bang' approach which turns the heat full on or full off. PID tuning lets the system figure out what heating rates to expect instead of the default values that may not apply.
I was having the same issue, my print bed is a 12" x 12" x1/4" aluminum plate, and was heating at about 0.3C/second instead of the 1.7C/sec the system was expecting.