Lock does not restrict access to custom "memo" tagged value

[amacara1]

Please, I am facing this weird situation: I have a number of custom stereotyped elements that feature tagged values I have also defines. Some of these tagged value types are of type "memo". For a couple of such "memo" custom types, locking access to parent folder does not restrict their editing. All non-memo fields of the same elements have access restricted and other tagged values also of "memo" type are restricting access.
What have I done differently for these types, please?

[amacara1]

I am using EA 16.0.1605