This is a power management issue combined with low latency tolerance of modern BT devices. The AR5BBU12 was not designed for Bluetooth 4.0/5.0 peripherals. Buy a dongle.
Follow this method precisely. Do not skip the “Show Hidden Devices” step. Bluetooth Module Atheros Ar5bbu12 Driver
The AR5BBU12 contains two separate devices: This is a power management issue combined with