Return it as it has a lifetime warranty. Microwaves have very different power outputs. Your appears to be a strong one. I'd use a infrared heat gun to monitor the temp and start a couple of levels lower. These can be bought very cheaply now. It's also one of my favorite kitchen tools that I use everyday. I'm giving away three this Christmas as stocking stuffers. They can be had for about $10-25 sans battery. iFixit has one with a lifetime warranty here: [product|IF145-249]
My original Fluke that I've used for 5 years was a Fluke at over $250: http://www.tequipment.net/Fluke561.html?Source=googleshopping&gclid=CKuvvNOx2ckCFYI7aQodcaECLw