If your car frequently disconnects from your KaiOS device, you can try unpairing the two and pairing them again and establish a new connection. You can do this by going to Settings->Network & Connectivity->Bluetooth->Paired Devices->Unpair Device on your phone, and then go to Bluetooth->Nearby Devices to pair with your car audio system again.
To ensure your car audio system is properly connected with your KaiOS-enabled device, the two Bluetooth profiles and their versions on both your car audio system and your KaiOS device have to match. Otherwise, either no connection is established or the connection is incomplete. We recommend comparing the profiles of your car and your KaiOS device. To do this, on your KaiOS phone, go to Settings->Network & Connectivity->Bluetooth->Paired Devices.
If the issues persist and all profiles comply with your car audio system, we recommend reaching out to the device manufacturer directly.