Getting a lot of "can't copy - source file is being updated"

That is a little strange… That is rclone asking for the modification time on a file twice and it coming back with different answers…

However it isn’t unheard of (eg with GlusterFS) so…

If you use a recent beta then you’ll find the

  --local-no-check-updated              Don't check to see if the files change during upload

Which will do what you want.