MX Keys and MX Master 3 sometimes will lost bluetooth connection with my MAC (running Big Sur) . For MX Master 3 it can reconnect by simple turn off and on my mx master 3 and it can reconnect back. For MX keys it is unable to reconnect. The only way to connect is to restart my MAC and turn off the MX keys and turn on again.

This is issue will oftenly occurs when using Flow features.