Issue using webUSB/serial in chrome 75 Mac

Clicking on Serial should open the REPL, this doesn't appear to be the case, though the micro:bit does say it's connected.
Recording of trying to connect

If I try to flash the device I get
"Error: Bad response for 17 -> 131 Please restart your micro:bit and try again"

Here is the console output

Have tested this with a micro:bit running 0249 and 0254 on Chrome 75 Mac

DETAILS TXT:
# DAPLink Firmware - see https://mbed.com/daplink
Unique ID: 9900000031634e45006e40020000005e0000000097969901
HIC ID: 97969901
Auto Reset: 1
Automation allowed: 0
Overflow detection: 0
Daplink Mode: Interface
Interface Version: 0249
Git SHA: 9c5fd81e6545d00b7f7c21ca9d8577dbd6a5fed2
Local Mods: 0
USB Interfaces: MSD, CDC, HID, WebUSB
Interface CRC: 0xcdb7b2a3
Remount count: 0
URL: https://microbit.org/device/?id=9900&v=0249

cc @microbit-carlos

No files or tests are named. Start by reproducing the connection in Chrome 75 on macOS with a micro:bit running firmware 0249 or 0254, then inspect the browser console and WebUSB/serial connection path. Done means clicking Serial opens the REPL and flashing completes without the reported bad-response error.

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