With my Hovabator 1588 and the dip switches (hate those things) I tried a long time to adjust it and the temperatures would bounce all over the place. I’d do something that the instructions said would drop it one degree and it would drop 10. Next minor twitch and it would jump even more. Talk about aggravating and frustrating.
Then I tried resetting it to factory settings. They give a procedure for that. But instead of flipping the #4 as they said, I flipped #3. It worked like a charm. So simple. The temperature dropped about 1 degree though they said it would only be ½ degree. You might try returning it to factory settings and flipping #5 instead of #4. See if that does what you want. Maybe #6 is right for you.
Once I did that the temperature has remained constant for years. I like my 1588 other than those dip switches. Changing that temperature adjustment was a good move for them.
Good luck!