Please try again using
this build.
As the files in /dev_bdvd are encrypted, it is required to call syscall 36 before copy to enable the access to the decrypted files.
The file_copy function calls that syscall automatically if the source path start with /dev_bdvd, but it didn't because in your test the source path starts with
//dev_bdvd.
In the
latest commit of wMM, the web command used to copy works fine again with /dev_bdvd. So it is not longer necessary to use
// in the path (unless you want to copy the encrypted files like in your test).