This question is similar to DocumentValidationException: Rule with path ‘/path/to/a/validation’: Iteration for ‘/a/model’ is specified, but the rule can fire for not filled repetitions of this repetition level so I an going to reference the models used in that post.
Modeling a similiar Computation Rule leads to the same error that you posted.
Adding the specification GroupFilled(/subsidiary/nameInLanguages) would normally resolve this but there is a modeling limitation that Rules relating to Repeatability need to be “in the same trouser leg”. What I mean by this is that your reference to the repeatable group cannot
- Go up to a parent group and then
- Down into a different group
This is described in the Documentation in Example 3. (This relates to the Error field but the same is true for Computed Fields.
There is an open ticket relating to this topic, A12-15148.
Currently, there isn’t an easy modeling workaround as you need to model this rule in the group “Angebot” and, as this is an include, it is not possible.