Thanks!
Can you try with -vv --dump responses What I'd like to see is the HTTP request which causes the error and the response with the full error message in it. (You can see which was the HTTP request because it will have an identical hex number to the HTTP response).
This will be print quite a lot of stuff!
It sounds like you aren't encrypting the file names - is that correct?
Do rclone config show remote to find out.
I edited your post to put the text in ```triple backquotes``` which is the best way of putting logs up.