Need help!

Recently my garage door "red" sensor flashed faster at the beginning, then low, then lower,then I have to wait until 15 mins without no flashing then to close the door!

Below are 2 videos about my flashing sensor problem:

faster: http://youtu.be/Px8kTZ4O8V8
(about 3 flashes in 2 second,)

lower: http://youtu.be/UR5dENOOZgE
(about 3 flashes in 3 second, then later 3 flash in 5 second)

My green sensor is always on, no problem!

The brand of my sensor is "Genie".

What's the problem with my red sensor??

Should I buy a new one ?