The battery contact terminals may be contaminated, causing a poor connection, so the device thinks the batteries are dead.
Test the batteries with a battery tester to confirm if they really are dead or not.
If the batteries really are dying quickly, then there is a short somewhere causing them to drain.
Yes I am familiar with these organs.
If the batteries are indeed dying quickly (and they are fresh and not out of date) then there is a short somewhere within the organ's circuitry causing it to quickly drain the backup battery. To find the cause of the short will require taking lots of test readings with a voltmeter on the board; alternatively the board could just be replaced.