I recently bought a Thunderboard Sense. I placed it on a flat surface, calibrated it and read, n my smartphone screen a 0º bearing. Following, I rotated it into an opposite position, aproximately 180º. I obtained a 163º bearing. When I repeated the operation, I obtained another different reading and so on... It's impossible to reach a similar reading in a similar position. Is there any bug somewhere, or it's a Thunderboard's malfunction? What must I do? Thank you!