My t-stat (current room temp) reads between 2 & 5 degrees higher than the actual room temp. It seems when the stove starts pushing heat at night the (current room temp) reading on the t-stat will gradually go 5 degrees higher than actual temp & as the stove slows down the (current room temp) gradually drops to 2 degrees above actual temp. This is over the course of several hours. Is this normal? Thanks.