HOWEVER, I have changed the destination folder to a random folder in My Drive (instead of in my Shared Drive) and it worked perfect. So might indeed be either some restriction on the SD, or some limitation in that case. Will continue testing.
Oh, to be honest I missed the shared drive part at first. I only tested this with one of my own folders.
Shared Drives are unfortunately not fully supported by n8n, so you might want to leave a vote on the respective feature request (and possibly add a comment that you’re using the regular Google Drive node here, as the conversation on that requests seems to be mostly about the trigger node).