Kitchen Aid not maintaining propper temp

I’ve viewed videos on refrigerator problems and think I’ve isolated my
particular problem to a bad thermostat. When I took the cover off our Kitchen Aid KSR W25FHBT I was surprised to find damper controls behind the freezer adjustment slide and thermostat controls behind the refrigerator adjustment slide, this appears to be backwards. The freezer and refrigerator are not maintaining the proper temperature despite numerous adjustments, freezer too cold or too warm -20 deg or +30 deg no middle ground. Any thoughts? Defroster timer seems to advance ok although it may stick? slamming the refer temp slide to highest setting seems to initiate the compressor cycle then get way too cold in freezer and refer. the temp slide for refer seems to stop or start compressor but correct temp is not achieved.