Do you let the chiller control the on/off? If so, I would have another method do it. There are some cheap controllers that you can put your heaters and chiller on with better thermometers than the chiller.
Not sure why it would jump other than they are not that accurate reading temps.
I have the same chiller and have for over 10 years. I have only ever really replaced the fuse and cleaned it out when offline in winter. Mine is run off Apex, but I just got a cheap controller to set up on my other tanks with my other chiller. I have not set it up yet as it has not been needed.