I've this heater for about 5 months now and I noticed that it no longer calibrates properly. The temperatures are a few degrees past the limit of the red dial so I now I just ignore it altogether and adjust accordingly with the blue dial and a thermometer. There is also quite a bit of condensation that has built up inside the heater. Is this normal? I remember reading a thread where Eheim claimed that the condensation was from the oil that's applied inside.