Back when I was using the styro-bators, I tried several types of digital temperature gauges. I got a couple for reptiles (temp and humidity), with the cords, and probes on the ends. They would work pretty good, for a hatch, or two. When the batteries would run down a bit, they decreased in accuracy. I got the digital kind you set in the incubator, just temp, no humidity. Again, they did good at first, but as with the others, in a short time, they too decreased in accuracy.
Along with the digital ones, I put in a cheap Little Giant alcohol thermometer. Those stupid Little Giant alcohol thermometers cost me about $6.00 at the time, and were the most reliable, and they were consistent.
Over time, I've accumulated quite a few of them. My R-Com incubator, so far has always been spot on regarding temp, and humidity, but I still put one of those cheap alcohol thermometers in there. I also use them in my brooder(s), (taped to the side, at the bottom) so I know what the temps are in the warmest part of the brooder.
It would seem the general consensus is that the Spot Check is one of the most accurate, and reliable digital thermometers out there. I've never used one, but I think that's what I'd go with, if I needed a digital thermometer. Sooner or later, all digital thermometers have to be replaced. Some, a lot sooner than others. You've gotten quite a few years of good service from you Spot Checks. It's simply time to replace them.