A little bit of update:
it seems that even i don’t have tabs, the JS responsible with this is this called. So if i disabled acf.fields.tab.show_tab_fields and acf.fields.tab.hide_tab_fields mehtods, things starts to work better (although still buggy). Keep diging.
Here is a very simple example: https://gist.github.com/069f7c64781a906fd02e
(and xml export: https://gist.github.com/2a0840fa93bdf898de56 )
