Splitscreen Not Working on Nintendo Switch

After downloading Minecraft 1.19.20 on my switch, I tried playing splitscreen with my sister on my  60MB world created in 1.18 as I do almost every day. When I entered the world by myself, everything seemed fine, until my sister joined. Her side of the screen was completely black, and my side was freezing. I assumed this was just some normal lag, but it lasted about thirty seconds, and so I took out and reinserted the game card, and closed the software and then entered my world again, same result. So, we just played on our much smaller, side-world created post-1.19, without any issues whatsoever. Does this have to do with the size of world or is this just a bug?