My mendelmax 1.5 is fully assembled and seems to be operating correctly except for one problem. Directly after plugging the printer in, the heatbed rises to 55.5 degrees and then falls (without any command to do so). This process is out of my control before, during, and after the rise and fall of temp. I have replaced the the thermistor - as well as the RAMPS1.4 and arduino boards for unrelated reasons. I switched the extruder thermistor-wire and heatbed thermistor-wire on the RAMPS 1.4 in hopes of tricking the process, but the same cycle still takes place. Any ideas?