Problems with stacking values in the time-series-panel

I’m using Grafana v8.2.4 on Ubuntu Server. I have the values of 3 power phases (Germany, don’t worry) and want to combine them on top of each other (so essentially a stack in the Time Series panel) to see what the total power is.

Unstacked the graph looks like this:

If I now turn on stacking I get this:

Normally the area below the lines of a graph should just be stacked and added on top of each other. I searched online for some time but didn’t find anything. I’ve also had this problem in a previous Grafana installation. Thank you in advance!

Zoomed in it looks like this: