I seem to experience troubles like that with any kind of Bluetooth devices. E.g., sometimes they don't connect or disconnect or lag. At this point, I am suspicious of the entire Bluetooth technology. The same is with WiFi actually: it does work well most of the time but sometimes it does not (for whatever reasons, bugs? changes in environment?).
I find Bluetooth to be the flakiest of the common technologies I use. There are just way too many times that it just doesn't work for no discernable reason.
I have 3 cars with Bluetooth and they all have their quirks, but they generally work. The Ford Fusion, which boasts the Sync system "by Microsoft" is the worst, though. It will always show the little Bluetooth icon soon after starting the car, but when you try to switch to your device, it says there is no Bluetooth device and I have to connect manually by selecting the phone (which Ford lovingly places behind about 8 knob turns and clicks). And of course, sometimes it simply refuses to acknowledge there is a phone at all, so we keep an analog audio-in cord handy.
And I have had a couple of different Bluetooth phones. My previous phone was a Samsung Galaxy 4 Mini that I replaced about 6 months ago with an A52. Bluetooth always worked fine with both phones, but again, there are quirks. In my Honda Civic, the old phone would automatically connect to the car's system and start playing whatever music I'd left off within about 20-30 seconds, whereas with the new (and much nicer) Samsung A52, it takes 2 or 3 minutes... or until I get impatient and select the phone manually.
