eBay has an coding error in the RegistrationAddress call by GetOrderTransactions.
[RegistrationAddress] => SimpleXMLElement Object ( [Name] => Thomas GÃ¶tz [Street] => ***** [Street1] => ***** [CityName] => ****** [Country] => DE [CountryName] => Deutschland [Phone] => Invalid Request [PostalCode] => ***** )
The Last Name of this Customer is "Götz"
In all other positions like ShippingAddress->Name or in the GetOrders Request it will be ok.
Please fix this, thank you! Have a nice day and stay healthy :)