How can we disable the automatic categorization of Yes/No fields in Omniscope Explorer?

Situation: a Yes/No field that has [Filter type] = "list of Categories".

When changing the source file in DM, this field is changed and moved to the Yes/No fields tickboxes.
Normally this shouldn't be a problem, but in our case it is because it is a frozen field selection.
When moved to the Yes/No fields tickboxes it isn't frozen any more and our endusers receive a error message.

How can we solve this problem?
Many thanks