Is my temperature probe malfunctioning?

[BigHildy53]

The temperature in my display tank occasionally jumps significantly. Different times during the day. This can't be correct, it's just too drastic of a jump. The probe is not next to a heater. Any ideas?

 

[BigHildy53]

I did not mean to include the second chart. Tmp is in the sump and Tmpx9 is in the display tank. I really don't like the way Apex doesn't display both temp probes using the same scale.