Hello there. This is interesting. I suspect that the rise before the
cooling is from the ammonia solution being heated to operating tempature.In
the "off mode" the ammonia solution is not warm enough to do the cooling
(sounds strange),but is very near warm enough. This needed increase in
tempature,for cooling, adds extra heat load to the rear of the frig.  I am
guessing that your probe is near the rear of the frig,and is picking this
up.You may want to add a small battery powered fan to circulate and even
out your readings.