'05 TT 3.2 strange brake "groan"

Hi all,

Just recently my '05 TT started making a strange noise under very
specific conditions. When the outdoor air temperature is between roughly 32f
and 50f, the car illicits a strange "groaning" sound when I use the brakes
while in reverse. When the air temperature is either warmer or colder there
is no such noise. And the car otherwise drives normally.
I doubt it's anything serious. But, with the weather getting warmer, I'm
afraid that I won't be able to reproduce the issue when I bring the car into
the dealer next week. So might anyone here have any idea what might be
causing this "groan"? Or perhaps know of several things to look at regarding
it? I figure it will help with the diagnosis if I can tell the where it
might be coming from.

Also....an unrelated question while I have your attention.

Within the past week the car started doing another odd thing -- or
rather not doing it. Typically, when you press the "lock" button on the
keyless remote, the horm chirps to confirm that the car is indeed locked.
However, it has stopped doing so. When I press the "lock" button, the car
does lock and the alarm indicator lights begin to flash as they are supposed
to. But the horm doesn't chirp. I don't think that it's a case of a bad door
sensor, because as I said, the alarm is visibly arming itself when I lock
the car. So what could it be? Might I have unwittingly changed a software
switch that enables/disables the horn chirp? I'm at a loss.

Thanks in advance for any assistance or ideas you might have.

Rob
2005 TT 3.2 DSG
2002 A4 3.0Q