The temp swings are ok... I have a 55 and it’s not that ‘old’. For example, if I set mine to 225, it may swing from 185 to 265 but the average is usually close to 225 and once I discovered that, I never worried about it. I assume your 150 is not a typo so that’s not correct. One thing to check would be the temp probe which is on the back side of the cook chamber. Make sure it is clean and you never put your product up against it. Other than that, I’d call Cookshack for help.