The authentication failure happens on some dual-mode devices, where the LE advertising events are received earlier than the BR/EDR inquiry reports. Given this fact, if the major service is provided through BR/EDR connections where the BR/EDR inquiry report has not yet received, the users will encounter authentication failures during pairing until the  BR/EDR inquiry report is received. And the time difference between LE discovery and BR/EDR discovery is caused by the fundamental design of two technologies, where LE advertises in 3 channels while BR/EDR broadcasts in 79 channels, so it takes much longer for the central device to come across the same channel and pick up the packet in BR/EDR.

We observed authentication failures on Bose QC 35 and Bose SoundLink II if we clicked on the device within the first 5 seconds of its appearance.