Hi, welcome to the forum.
This sounds like a problem on Jottacloud's part. There have been occasions of this before, if you search the forum you should find e.g. this: Errors with Jottacloud, although I'm not sure if there are any exactly the same as yours..?
Did you see the file in web interface, or official client? And got an error when accessing/downloading from there? If so, I would report that to Jottacloud without mentioning rclone.