I love Eiheim products but I'm not able to find much help on this product from their limited manuals. Most of the website downloads are in German. My local store guy isnt helpful. Can anyone with experience using this product help me with this strange problem? The heater stops suddenly. Then if I unplug it & change the temp, it starts working again. I notice the interruption only when fish look a bit uncomfortable as plants hide the indicator. Is this because I didnt calibrate it properly? Can anything be done Or should I return this product? It's been over week since I bought it - the store said 3 days for returns only. Thank you in advance!