Multi-sensor on front door keeps triggering SHM alarm

I’ve been using the multi-sensor on my internal front door, I have a porch and an external door between this.
It’s been working fine for over a year, but suddenly I seem to be getting Alarms trigged in Smart Things saying “Alarm at front door” (my multi-sensor has been named “front door”). Looking at the recent tab, it seems to show “ACTIVE” just before the alarm triggers. What would cause this to suddenly start happening?

Check the battery level.

Does it work properly if you open and close the door?

Are the sensor and contact lined up properly? Something may have shifted and you’re at the very edge of the magnetic sensor’s range.

Do you have “Front Door” set up as a motion sensor, or just a contact switch. “Active” means motion was sensed, not a contact opening. The Door settling and being able to move with the wind can start this happening, or a slamming screen door. A knock also.

Thanks for the comments. I replaced the battery and it has stopped.