So I had experienced the same intermittent disconnect between the iPhone and the BT module in the TT. Had it powered and wi-fi off.

Disconnects were worse the closer the iPhone was to the Nav i.e. like if I put the iPhone in the ash tray. But it was best when placed in the rear cup holder.

What totally solved the disconnect was when I turned the iPhone upside-down in the cup holder so that the antenna section (black plastic on the back of the iPhone) was exposed.

So if any of you are still having the issue, try the upside-down iPhone is the cup holder!

Also, if the iPhone doesn't want to re-connect, turn off BT in the iPhone and then reactivate it. For some reason that tends to wake it up.

Jeff