Hi,
I reread the documentation and the thing I missed in there is that Gerrit will only automatically rebase a patch when submitting when none of the files it changed have been changed between the parent commit of the to be submitted patch and the current top of tree. At least this explains the difficulties I ran into so far; I was expecting Gerrit to always try a rebase and only require a manual rebase when there is a conflict it can't resolve on its own like it was the case before. This makes both treewide changes and submitting patch trains patch by patch more difficult.
Regards, Felix