Whatever is happening, the initial statement sounds like follows:
- New version of user space software “notepad” (klippy host), makes the host hang
- New version of MCU firmware for USB-connected peripheral makes the host hang (I got a new flash drive, and it makes my PC hang).
Whatever is happening, neither the host-side code nor the firmware side can do that.
IIRC, RPI3 has some USB quirks, and the only known workaround to me is DWC2, whatever option: PI freezes after setting mcu USB id - #8 by Sineos
Hope that helps,
-Timofey