Very long WebUSB full flashing time in Raspberry Pi 4

[microbit-carlos]

Bug Description

Not a lot to reproduce at the moment, need to spend some time with a Pi 4 to see if I can replicate.

In essence at the PyCon Uk 2023 kids days we had some Raspberry Pi 4, which we used with the Python Editor, and a WebUSB flash took 5 to 10 min.

Not sure what the bottleneck was, as the UI was fairly responsive and partial flashing took a "normal" amount of time.

How To Reproduce

No steps yet.

Expected behavior

A full flash to not take longer than 2 or 3 minutes?

Screenshots

N/A

Environment

TBD.

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context

TBD.