Field BSEG-MANST. does not exist in the screen SAPMF05L 0301 in mass update

Hi,

I am trying to perform a mass update of dunning data (level and date) on some open items. Using the mass change function through FBL5N, I receive the error message, and the update is not performed. I cheched with the layout editor, but the fields appears in the mentioned screen. The field is also allowed for modification in customizing, for the company code. I was not able to find the dunning fields in the field status editor, in customizing.

Any hint?

Thanks

Massimo