Multi purpose sensor

I have a multi purpose sensor on my kitchen door. Whilst at home the sensor registers correct. Ie. Open, closed. But when I leave the house and smartthings is armed i receive a message and notification that the door is open even though it is closed. Does any one knows how to correct this. I’ve done the obvious disconnected and reconnected the sensor 3 times but with no success.

Most likely it’s not working correctly while at home either. Unless you have an app to monitor while at home mode otherwise you won’t know unless you look at the log. While you are away and armed. It will reports when open is detected.
I still have a couple of ST multi sensors and not much false alarm but because I went crazy with my zigbee mesh by adding tons of hardwired switches/plugs.
You could get involve with support and ask them to look into your mesh and that sensor. They should be able to help. Just incase. How’s the battery?

I bought a new battery. So it’s currently at 100 percent. I monitor it whilst at home using the smartthings app. If I open the door it says open. If I close the door it says closed. Plus I use it to turn the kitchen light on when I go into the kitchen and that works as it should

Send support a note,, but most likely the sensor is reporting open at the time you are arming Smart Home Monitor. How are you arming SHM? Through a Routine?

When I leave the house and get a certain distance away smartthings performs ‘goodbye’ and arms. I get a notification that this has been done. Then immediately I get another notification and a text message to say the kitchen door is open

If you look in the app when you get that notification, does the kitchen door show as open?

Yes. It shows as open. But I can assure you in reality the door is closed