mkvproedit unable to open file

[Quitch]

I'm trying to change the default subtitles on a number of .mkv files. Thanks to the_weirdo I've put together the following:

FOR %F IN (C:\users\user1\folder\*.mkv) DO mkvproedit "%~F" --edit track:s1 --set flag-default=0 --edit track:s2 --set flag-default=1

I see it successfully find both files, but both result in the following error:

"blah.mkv could not be opened for reading and writing, or a read/write operation on it failed: open file error."

What's going wrong?

[the_weirdo]

You must change current working directory to the folder that contains MKVs for that command line to work. Alternatively, you can modify your command line to this:
FOR %F IN (C:\users\user1\folder\*.mkv) DO mkvproedit "%~fF" --edit track:s1 --set flag-default=0 --edit track:s2 --set flag-default=1