–auth-password is not supported gives a simple way to stop your warning (even though it’s a different one).
Changing backend type leaves invalid backend options #3082 is the issue (awaiting a JavaScript volunteer)
Error seems more suitable. I don’t know why it’s just Warning. Was this whole backup uploaded by rclone? Everything else turn out OK, although one error out of a whole lot of them is still one bad upload too many?
To confirm, rclone is set up for native pCloud, not WebDAV, right? Attempting to bypass the WebDAV error.
Possibly though, it’s a generic pCloud issue. Before concluding anything, want to understand the test done.