FireLite MS-10UD glitching when ac power removed

Fire Alarm Help
1

I have a FireLite MS-10UD that works perfectly fine and is trouble free as long as ac power is connected. However, when I remove ac power, the ac power light starts glitching as well as the backlight to the display. While it is doing this the piezo beeps in a strange pattern and cannot be acknowledged. The second I reconnect ac power, it goes back to normal and works fine. Here is a video: Video
I know the cover says 5UD but I know it is 10UD.
If anyone knows what the issue is or how to fix it please let me know.

4

batteries are brand new and are fully charged

5

I don’t have a lot of electrical knowledge at that level, but obviously something ain’t right there. Do you have a multi meter perhaps you can use to help troubleshoot? Batteries look like they’re sized right for that panel.

6

I did test the batteries and they put out a total of ~25v, but I can test to make sure they are still good when ac power is disconnected.