Grabbing keyboard breaks its built-in mouse on MacOS

[QuentinI]

I am using a CharaChorder 2, which presents as a composite HID device. Grabbing it with keymapper and remapping keyboard keys works great, but the mouse keys become completely unresponsive.

[xiexingwu]

Mac user here, had a similar issue where my mouse stopped working. I think it's because some (modern?) mice are recognised as keyboards by MacOS.
My workaround was to skip all devices and only grab the Karabiner virtual keyboard, i.e. this is on the top of my keymapper.conf

@skip-device /.*/
@grab-device-id "pqrs.org:Karabiner-DriverKit-VirtualHIDKeyboard"

Hope your PR #321 addresses the root cause!