Even Worse, I just found out that OpenType (OTF) Files behave the same way.
Then Windows fails to find the required font driver from Adobe.
sfc/scan
It checks if there has been changes to important Files of Windows and replaces them with original versions if necessary. It seems like it WAS necessary. Now it works! Thanks for your help anyway. I was devastated as I tought I had to reformat the system…
I’m glad you’ve solved the issue, thanks for sharing. So it seems Windows failed to load the font driver from Adobe, because it was corrupt.