Hi Martijn,

I reproduce the first problem with Mathematica 13.0.0 and 12.3.1 on Windows 10 x64, but not with Mathematica 8.0.4 on the same machine. Apparently, it is a regression bug. Please report it to the support.

As to the second problem, I recommend using Grid instead of GraphicsGrid for such purposes. It is well-known that GraphicsGrid behaves poorly in many respects, and it is recommended not to use it at all (but you always can try searching for a workaround for your specific case on MMa.SE). Apart from Grid, you have such a wonderful alternative as PlotGrid in the WFR:

https://resources.wolframcloud.com/FunctionRepository/resources/PlotGrid