The objectadmin doesn't work properly in a language other than english.
At least the buttons on top of the admin don't work.

E.g. the buttons from attributes.aButtons do have a localized value, e.g. "Hinzufügen" for add, "Löschen" for delete, ... e.g. in the german language.
Due to this fact, the <ft:processForm action="add" ...> won't match, because the submitted value is in a different language and the action asks for English.

The simplest way to come around with that would be to change the processForm tag to:
<ft:processForm action="#application.adminBundle[session.dmProfile.locale].add#" ...>

The dropdown boxes for each object are not affected, because they are not localized (yet).

Short term fix:
Change lines 159, 173, 374
to

<ft:processForm action="#application.adminBundle[session.dmProfile.locale].delete#" ...>
<ft:processForm action="#application.adminBundle[session.dmProfile.locale].unlock#" ...>
<ft:processForm action="#application.adminBundle[session.dmProfile.locale].add#" ...>


Long term fix:
change all of these processForm tags and localize the drop down boxes too.