TasIS200

Hey guys, I have a 2000 IS200 with a faulty alarm. I have had the car for a year now and the alarm has started to go off when I lock it, with no regular pattern. I have taken it to Lexus and they used a diagnostics tool to find out what was wrong, but couldn't determine what it was. They said the radar sensor in the interior is fine, the door switches are fine, and that the alarm seems to be fine. Has anyone had the same issue? They recommended a bonnet switch replacement. Any ideas? Cheers.