There isn’t any unusual type of coating which would be harmed by a dishwasher since the inserts are ceramic. Ceramic coffee mugs go through the same firing process when made and they certainly go in a dishwasher far many more times in than crockpot inserts.
The firing process for ceramics and their glaze coating uses incredibly high temperatures far in excess of the water in dishwashers.
The problem is that the temperature of the cooker itself is higher than it should be. I had this happen to me with Spaghetti sauce in a cooker I bought on Craigslist. There was obviously enough liquid in it and i had it on LOW the entire time so the only other thing was that the temperature was running too high.
But it was a Westbend not a Rival ( the originators of the Crockpot and the only company legally permitted to use the term Crockpot)
And after that experience with scorched sauce, that’s the only brand I will ever buy; Rival Crockpot. I’ve never had scorching in any Rival I’ve had over the years on any setting or even with little additional liquid. Theirs have always been calibrated correctly.
So if yours has the Rival name on it, in all likelihood the thermostat is defective. You should call Rival and tell them of your problem. They may replace it for you. They’re a company with a reliable reputation and stand behind their products.
If yours isn’t made by Rival, I don’t know what to say since other brands have such variabilities of temperature range.
I’ve read forum posts by folks with various other brands and this complaint about scorching is not that unusual for OTHER brands.
It matters little how great the recipe nor how faithfully it’s followed if the problem is with the appliance itself running at the wrong temperature.