After downloading the updated project and immediately upgrading from 4.10 to 4.11 and building did in fact give me the same crash you mentioned. When I tried to revert back to 4.10 I got the same errors about the GENERATED_BODY() line.
Since I am having difficulty testing from one version to another, can you try opening the 4.10 version and setting the default loading map to a level other than NineRooms and then convert to 4.11. If you’re able to open the project in 4.11 after this, also let me know what happens when you double click the NineRooms map or right click on the asset in the content browser?