This study spent a long time proving that insulin in a regular fridge is often exposed to temperatures outside its official storage range (as if it came as a surprise to most of us):
Medical News Today: Diabetes: Fridge temperature may make insulin less effective.
Unfortunately, they appear to have forgotten to prove that such temperature variations would impact insulin efficiency… Their conclusion:
Dr. Braune […] warns, “More research is needed to examine the extent to which temperature deviations during domestic storage affect insulin efficacy and patient outcomes.”
Bad logic = bad studies