Incorrect rendering in vertical/deskbar panels
Starting from xfce4-panel
v4.19, when placed in a deskbar (or vertical) panel, the systemload plugin bars ignore panel width and render into an arbitrary size.
I.e., unless the only row that's enabled is Uptime Monitor, what I see in the panel looks like this:
In order to see the plugin properly, the panel needs to be stretched to about triple of that width: