"In the beginning, Rival created the crock-pot .... and it was good!" ... and recipes were written for it. It also had one temperature setting - about 185-200-F.
Then came the early "Renaissance" period in slow-cookers - 2-temp crock-pots (200-F for Low and 300-F for Hi). Now - they are a mess with probes and timers that may have nothing to do with the recipe you are trying to use! The problem is that there are a LOT of old (LOW only temp) crock-pot recipes out there that folks with 21st Century (multi-temp) crocks are having a problem using.
If you are consistently having a problem with the food being "overcooked" the only logical explanation I can think of is that the cooking temp is too high! Unless the recipe explicitly states a certain temperature setting - use LOW if your pot has multiple settings.
"It ain't what you don't know that gets you in trouble. It's what you know for sure that just ain't so." - Mark Twain