If you load into a realm, wait about 5 seconds whilst it loads and then click cancel, then immediately load into a server from the 'multiplayer' tab, as weird as it sounds the realm world and server will practically combine. Since you click cancel after waiting, the cancel button doesn't work properly and still loads you into the realm. Then since you load into a multiplayer server, some aspects from the realm carry over to the server and all the chunks will fail to load. This seems to often lead to a game crash. The things that carry over seem to be mainly data packs and sometimes items. (As an example, I have a co-ordinates hud on a realm, which it tried to use on the server). It's not game breaking but just thought I'd mention it.