supertab integration problems

I have the newest vim-pandoc, vim-pandoc-after and supertab installed in .vim/bundle for pathogen.
In my .vimrc I have

let g:pandoc#after#modules#enabled = ["supertab"]

Completing a citation key works with , but not with . But after I used I can cycle with . When I stay in insert mode I can even begin with a new citation key with "@" and then use . When I leave insert mode and enter it again, it doesn't work anymore. Only after using .