In reply to @jviega "On my phone but": I made triple sure, recompiled with
additional debug output in places where the code arrives and the result
(NTSTATUS) is.

There was indeed a mistake. However not the one you expected nor did a fix
change the Nim outcome. In the Nim code i posted i used winim widestring. Which
probably called CreateFileW. It worked somehow but status was bad parameter.

After changing that the debug now results in a 0, so everything works. However,
all of this still crashes with SIGSEV in debug versions