vfs: error when opening files from constfs filesystem

[maikerlab]

In my RIOT application I initialize the constfs file system and some private data in a c-file, exactly like in the filesystem example (with vfs_mount).
I can also open and read the contents inside the file (e. g. with fopen("/const/dac", "r") and open("/const/dac", O_RDONLY))
Reading from shell is also possible (e.g. with vfs r /const/dac 15 0)

In my Rust code, I first call the external C-Function, where vfs_mount gets called.
When iterating over all mount points with vfs::Mount::all() and files inside /const, everything looks as expected and the desired files exist.
But when trying to open a file (e.g. with vfs::File::open("/const/dac"), I get an error (-2 ENOENT 2 No such file or directory)

I could reproduce this error on native and nucleo-f429zi board