Bluetooth & busy signals?

I have a Motorola brand Bluetooth headset and a Motorola V551 phone. All
has been working fine. I had an experience today though that while using
the headset if the phone number I dialed returned a busy signal I could not
hang up the call from the headset and had to do it from the phone directly,
it works fine in all other cases. I simulated that situation many times and
always get the same result so I know it wasn't the area or anything like
that. Has anyone else experienced this? Is there any workaround?

Thanks in advance... Fred