Is that a privacy-fixed original source path of the one .bak file you want to restore? It looks like there’s an attempt to remove the common folder prefix, given multiple files, and possibly it’s confused by single file. From the FILETORESTORE.bak content, I’ll assume that’s indeed the needed file, and not a folder path.
I suspect it’s getting the error on that last return by trying to take the portion of the path after the prefix, but when the prefix is everything, that’s too late to be starting because there’s nothing left. A workaround may be to force the first return by not giving a --targetpath, assuming the drive letter is the same and there’s no conflict with a new file. See my question just above trying to understand the .bak file usage on new server.