Error closing serial port

[synalysis]

When I try to put the firmware on macOS on a T-Echo the firmware can be uploaded completely but then closing of the serial port fails and the firmware is not installed.

entering dfu mode / index.html:977
entering dfu mode: done / index.html:980

Sending DFU start packet / nrf52_dfu_flasher.js:172 
Sending DFU init packet / nrf52_dfu_flasher.js:175 
Sending firmware / nrf52_dfu_flasher.js:178
Closing serial port / index.html:1039 
failed to close serial port, ignoring... TypeError: Cannot read properties of undefined (reading 'close') / index.html:1043 
    at Proxy.flashNrf52 (index.html:1041:43)
    at async Proxy.flash (index.html:992:25)