this won't really help but -
when i had garmin 2820, autocom bt dongle, sony phone (various). the connection would drop in and out - it was rubbish - you would you to "force" the pairing each time....
now i have -
garmin 2820.
autocom bluetooth dongle. (the same one i had with the sony phones)
apple iphone.
all the hardware is mounted in the same place as it was when i had problems, sat nav on bars, BT dongle to right of fuel tank just below and behind the bmw logo on my 1200gs, iphone centre fuel tank below fuel filler.
set up works fine now - always - auto pairing - constant connection.
my point is the only hardware changed has been the phone..........