We encountered this strange behavior during testing linking both an Android device and a Google Play identity to an account.
After a device ID was linked to a profile using LinkAndroidDeviceID with ForceLink = true (in addition to an existing linked Google Play identity), and the device attempted to log in, instead it ended up creating a new profile. In the web interface both profiles - the one linked and the new one - appear to have the same Android device identity.
Profiles with duped identities:
F195769E9DD91AC6 and E97B6D4A88356EA6
8BA2B0B1E07711E0 and 8715A08B58A0EF56