HI temps ==> medication integrity (It's both heat and LIGHT labile)
LOW temps (and other environmental insults like salt water, repeated x-rays, etc) ==> mechanism. But also the seals can fail (extremely high temperatures also come with this concern), which can also lead to degradation of epinephrine via oxidation.
Just for clarification, either thing is obviously not good. But my impression is that as long as the device and mechanism have good integrity, fairly frequent excursions into higher-than-ideal temps (meaning 80-100F) aren't that big a deal. VERY high temps obviously are. EVERY low-temp excursion (meaning down to something near freezing or below) is a risk because of cracking in seals.