Hi Sven,
I’ve experienced similar when publishing to our own on-premise ORCH. It turned out to be an issue in the IIS which was not allowing packets to be uploaded to it greeater than 50K. If your problem is the same you might want to take a look at this thread: (413) Request Entity Too Large - #5 by KlausA.
At the bottom is what helped me. Maybe you can ask your AWS admin to help you with that.
Best greets
/Klaus