Baerlax:
what would a delay in the setup achieve, when the error only occurs when the loop repeats the second time?
I wasn't going to try reading that code, so I just said "implies". You are right, the 85° can be fixed by changing the order of commands. It will also go away simply by having a longer setup section, which boils down to much the same thing. An SD card check and an associated display might provide an adequate delay.
The error can occur in the second trip round the loop simply because the loop is too short, but the time to the point in the loop plus the setup time was sufficient. I would imagine that, if you got that, you would get 85° on all the subsequent readings as well.
IF the subsequent readings are kosher, i.e. you only get one 85°, I'm afraid I have no explanation, as that implies the loop is actually long enough. I guess it must be down to wiring or power supply, but it might be code - caused by changing the length of the loop.