Ok, turns out that https://bugzilla.libsdl.org/show_bug.cgi?id=4389 is a different problem (there the game locks up permanently and the machine needs to be rebooted for it to even work again and also it’s Win10 while here it’s Win7).
I created https://bugzilla.libsdl.org/show_bug.cgi?id=4391 for my problem.