Bed and nozzle temperature jumping During my last print I noticed this jumpy behavior during heat up (blue is bed, red is hotend):



So I am wondering about the jumps. What could cause this? I do not think that it is a defunct sensor (it is in both sensors) and I also don't think it is real. Could this pose some sort of hazard as temperature might not properly be controlled?

I use an Anet A8 printer with Marlin 1.1.9 and Octoprint
Since the terminal temperatures never exceed the setpoints, there's no apparent potential for disaster.   Whether it's due to missing readings or to some sequencing of power (current) applied to the bed vs. the hotend, it really doesn't matter.   

If you have a similar graph of the temperatures over an hour of printing and you see signifcant anomalies there, that might be of interest.