Well, I would up the temp then, just a bit. Let it go to 98, then go by the feel. With your wrist..does it feel like a baby bottle ready to be taken? If so, go a little higher, of course, if it's too hot, then go back lower. This is how I work my temps without those fancy thermometers. I get to know how the eggs feel in my hand as to where I want that thermometer to read. Right now, I have one bator at 100, the other is 99. The eggs feel the same to me warmth wise. This took a couple of yrs. to do, by feeling the eggs warmth. Just a thought, you can buy another thermometer to go beside the other one inside to see if it's off quite a bit side by side.
I do this same thing--after raising a herd of kids...I just go with the "if it feels like it has a fever the bator is a tad warm lol!