You can see how at the top of the screen, the lines are somewhat cut off. This is taken at a zoom level of 51%. The space normally looks like this:
Public link to the space - I can repro it slightly in an incognito window. Zoom out, make the window small, and you should at least see it applied to the pink lines.
I have encountered this in a more extreme form before, where lines were not showing properly on the majority of the screen when at the top of the space. It was in a larger space, maybe the size/height of the space has something to do with it?