Operation /modelgroup/createModelGroupByPath fails to create provided model group

When deployed as part of the ADOxxWeb API the /modelgroup/createModelGroupByPath operation fails to create a model group.

In this case the used input for modelgroupname was Models/Testing/New-ModelGroup. Both the "Models" and "Testing" model groups already exist:

Details from execution through Swagger:

It appears that there is some issue with the AdoScript used for the operation, cutting off too much from the input (initial M missing) as well as ignoring parts of it (New-ModelGroup missing).