<p>During my last print I noticed this jumpy behavior during heat up (blue is bed, red is hotend):</p>

<p><a href="https://i.stack.imgur.com/KlD2K.png" rel="nofollow noreferrer" title="Graph of heatbed and hotend temperature over time"><img src="https://i.stack.imgur.com/KlD2K.png" alt="Graph of heatbed and hotend temperature over time" title="Graph of heatbed and hotend temperature over time"></a></p>

<p>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?</p>

<p>I use an Anet A8 printer with Marlin 1.1.9 and Octoprint</p>

It looks like everything is ok with the real temperature, and it is just Octoprint missing some readings, like Oscar said. 
But I think it is unlikely the USB cables fault, the whole print would fail in that case. I think the PI is to busy, maybe due to a Webcam streaming at high rate (try reducing the framerate). Another reason might be if you use a PI Zero W, especially if you transfer data over the Wifi at the same time, since Wifi and USB cause bottlenecks for each other on that board.
PS. I'd comment, but don't have privilege yet.