ademco 5890 wireless motion detector stopped working

[ymg200@xxxxxxxxxx]

Hi all,
I wonder if anybody has experienced this before or I'm the first one.
I have Vista-20P for few months already. I have never changed the
configuration since I programmed the system few months ago. One of the
sensors - wireless motion detector 5890 stopped sending alarm signal
about a week ago. It is not dead though - if I open the sensor it
triggers temper alarm. So batteries are definitely not dead and the
system does recognize it since the system reacts on the temper switch
inside the sensor. Also, if I put the sensor into the Test mode, red
LED on the sensor lights up upon motion. It looks like all features
work except sending alarm signal upon motion.
The sensor was originally at the Zone12. During troubleshooting I
deleted Zone12 and enrolled this sensor at Zone13, but result is
exactly the same - temper switch does trigger temper alarm, but motion
detection does not send alarm signal. This sensor has Zone Type 1
(Entry/Exit), Partition 1, Loop 1
I appreciate any tips. I don't know what could be causing this problem.