Text height/font of a dimension (with annotation) is fixed

Hi,

I have the problem of a dimension with annotation activated and a connected textstyle. So far so good, only that the text heigth becomes a different height (despite the values set in the dimstyle or textstyle). Furthermore neither Font or Text height can´t be changed (it jumps when clicking in OK back to the values in default).

Has anyone a clue, why the values can´t be changed?

Thanks,
Ingo