The USCG just issued a safety bulletin regarding the use of the wrong batteries in safety equipment and how that might make the device fail. Even though the USCG document does not state exactly what happened here is my take.
The light was an ACR SM-2 which was designed to use a standard carbon battery. Someone installed an alkaline battery which sounds like a good idea but it weighs more. As the bulletin states, the device label has the correct battery options listed.
Here is the USCG notice: SM2-Battery
Please take the time to read the labels and use the proper batteries in all your life saving equipment.