Seen most commonly with some smart card readers, but likely plagues other devices that may not populate serial numbers, the sticky bit/always assign when set to one device will match multiple devices. This only occur with automatic assignment, as policy can't match USB bus/device since it will change across hotplugs of the device or changes in the USB topology. Manual assignment only uses USB bus/device ID, so it is unaffected.
Prevent setting the sticky bit if the device will be seen as ambiguous
Only prevent automatic assignment if device is ambiguous
This allows automatic assignment of a single device that would be ambiguous if multiple units were connected.