Garage door remote control constantly transmitting??

["noblehouse" <noblehouse53@xxxxxxxxxxx>]

My condo building has a gated underground garage.  All owners have a
remote control to open/close the gate.  We have been having an
intermittent problem with the gate opening repeatedly.  That is, it
closes a couple of feet, the opens again.  It will do this constantly,
for hours if we let it -- sometimes it will stop on its own, sometimes
someone will put a piece of tape over the beam so that it just stays
open.  .

The repairman tells us his theory is that someone's remote is "stuck".
If this is indeed the problem, he has not been much help in tracking it
down.  One of our homeowners is eager to enact a plan where we take
turns monitoring the garage, note which cars are there, who comes and
goes when, and correlate this information to when the opening problem
occurs, thereby tracking down the offender.  This seems overkill to me.
 Surely there is an easier way to detect where a signal is coming
from??

1.  If we go to the garage when the problem is happening and
temporarily change the remote code, then if the problem continues,
wouldn't that tell us that the problem is NOT a stuck remote, but
something else triggering the opening. (Like something is interfering
with the beam so it "thinks" there is an obstacle and it reopens the
door)?

2.  Is there something else we could use as a receiver, set it to the
same frequency as the gate opener, then change the gate code.  If the
door stops opening, but the second receiver gets a signal, then that
would tell us that someone's remote is transmitting.  Couldn't we then
use that to somehow track down the source?

I'm not knowledgeable about electronics and whatever technology makes
garage door openers work, but it seems there must be some way to track
down the source of the problem short of tracking the comings and goings
of our neighbors.

Thanks,