Went out camping this weekend with the temps reaching 95 degrees outside, our refrigerator could not keep up, never getting below 40 degrees. The freezer worked great, but when I checked the fridge, ...
Double check that the thermistor hasn't slid *down* while inside of the plastic holder.
Make sure your thermostat, that you're using, is accurate. The cheapie ones might be +/- 2* or more!
Our house fridge is set to 36*, so if you're below 40 now, you don't have too much farther to close the gap and could also be within the error of your thermometer.