Everything in the source and destination is alphanumeric, so I'm not sure if this issue is a red-herring or if there is actually something wrong with either the source or destination.
I'd post the --vv logs, but it's just repeated information with error 400 listed for every file.
I'm updating and going to retest once this system starts backup.
I was going to say the same as NCW. buckets have remote:bucket/folder syntax in their path
No idea why it would work with a slash before the bucket
maybe if you let us see your config file it might reveal something wrong NOTE!! Please redact any sensitive information before posting, such as client secrets, crypt keys ect.
I can't post the specifics of rclone lsd b2: as this would divulge confidential information, but it does list the buckets, and if I go into any of those buckets, I can see the contents.
As for the second line, I get a errors regarding permissions (mac formatted device with all of the stupid mac attribute files, but to summarize : permission denied) on those .spotlight, .fseventsd and .journal files.
Otherwise there is no first line besides Transferred: with the progress for the current total.