I recently purchased this unit and an up right freezer. I'm new to this part of the brewing, only done ales in my basement so far. Well I hooked the unit up by running the probe up through the drain hole in the freezer and it is in the back right corner of the freezer which is right next to my carboy. I set the temp the night before at 58 degrees, well I had to change the setting to 54 to reach the temp I wanted. Is this a common issue with these units? I was under the assumption that they were accurate and pretty much plug and play. Any insight would be appreciated and or helpful tips.