vt7.0.x: Edit Field Properties - changed label not saved

vt7 comes with the ability to change field labels in "edit field properties". At least "label name" is now an editable field. After changing the lable (doesn't matter whether it is a default or custom field) and "save" --> "Success - field details saved" is prompted. But it isn't saved then. Reopening field properties shows the previous label. Behaviour was checked on 2 installations in several modules and fields. All the same. The new field label is never stored/applied.