Kenmore/Whirlpool fridge temperature variations

We have a Kenmore side by side refrigerator (made by Whirlpool) that has lately started having some pretty good temperature variations in the refrigerator section. We have the freezer set at 0 degrees and the fridge set at 37 degrees. I have seen air temperatures in the fridge of as high as the upper 50’s and lows to around 37 or so. Recently, I read that it was better to check the temp with a probe thermometer in a glass of water (rather than an air thermometer) and the temp seems reasonably steady at somewhere between 40 and 45 degrees. We have had a serviceman out and he thoroughly cleaned the condenser coils and ran the diagnostic test - everything checked out okay on that. I’m wondering what the next step would be. The freezer is working fine and doing as it should, but the temperature variations concern me, and the fact that I’m getting 40-45 degree water temperatures with a fridge setting of 37. BTW - the serviceman did pull out the air duct/baffle and watched it while going through the diagnostic to make sure that it was truly opening and closing. Any advice as to where to go from here? The model number on this fridge is 106.56662500.