I have a 2009 scirocco tdi that I've had from new and the alarm goes off randomly, sometimes twice a day or once a week.
The computer says H12 Alarm Horn, but also interior sensor. The horn was changed under warranty along with central electronics module.
Also I get the bong noise that tells you your battery is low only when my radio is connected, I have removed the fuse to stop this.
I changed the battery to a higher rated Bosch a few years ago. VW no longer want to know.
I have scanned the internet and found similar issues not they tend to not say how it was fixed.
Anyone had this and got it resolved.
Cheers