I had a simular experience at My local shop, with a temp control device i recently bought, just couldn't get it to work, took it in told them what was happening, they asked a bunch of questions and started experimenting with it with My build, and it did what i told then it was doing, put my build on his device, same model as mine and it worked fine, His build on my device acted like mine did. And although he said my build was "good" he asked if he can do a rebuild on it and give me some pointers, which he did, they replaced My device. All through this they were friendly.