Sennheiser MOMENTUM Wireless M3AEBTXL Instruction Manual page 12

Using the headphones
12 | MOMENTUM Wireless M3AEBTXL
If you pair the headphones with the ninth Bluetooth device, the saved
connection profile of the least used Bluetooth device will be over-
written. If you want to re-establish a connection with the overwritten
Bluetooth device, you have to pair the headphones again.
Paired and connected Bluetooth device
Paired Bluetooth device (currently not connected)