Editing description APM attribute not possible in some cases

Centrasite Version: Community Edition 8.2.1
Administration / Taxonomies /Application / Asset Type Details / APM / Edit Attribute

When i try to edit the description of a APM attribute string type
In some cases this is not possible.

I get the following error message;

“Schema Name does not match with NCName definition of XML”

In some cases the field is filled with data, but other cases not filled with data.
I tried to change the description again after all other users were logged out the system.

it should be possible to change the description of such a description field.

It would be nice if you know a solution
Thanks in advance!