Consuming eBay's Taxonomy API OpenAPI v2 specification throws errors because recursive data structure are created.
FWIW, I have run into this a few times in the past with various swagger specifications.
My workaround has been to create an extension and code up what I need using .NET. Given these are usually comprehensive commercial interfaces, this manual coding eats up loads of project time. In some cases this extra and unnecessary coding, testing and maintenance makes OutSystems a bad choice for a project; certainly selling the "low-code" story becomes hard.