We solved the issue by removing an Adobe Native Extension called Mobile App Tracker. It was old and unused anyway. Today Mobile App Tracker is integrated in something called Tune.
I recommend making a search in the project directory with for instance the application TextCrawler searching "_ADBannerContentSizeIdentifierLandscape" among all file types and the context in which the issue lies should reveal itself. Most likely it's tied to the SDK or an extension like in our case. Good luck out there 😊