Hi, after resolving the issue in my other comment, a new one has arisen. When I launch the game, I sometimes get a crash on the first attempt. If I close the game and try again, it works every time after. If I wait a while without launching the game, the crash happens again on the first try.
Here is the crash log: 
Viewing post in Ritter Ultimate Event Spawner (RPG Maker MZ) comments
Some testing notes: Changing the preloaded spawn map to a different one with fewer (or no) events doesn't resolve the issue. Not preloading any maps resolves the issue (but causes my other below issue to come back, so isn't an option). Changing the plugin order in the list doesn't change anything (either making it first or last in the list overall). The number of spawn maps to preload doesn't affect it. While I do have other plugins enabled, which ones are or aren't seems to have no effect, though having many enabled makes this more common. If I enable different blocks of like 30 plugins, the crash will happen no matter which ones I enable. I think maybe it could have trouble loading the spawn maps when there is a lot of other stuff also loading from other plugins.
Another testing update: This is happening even when there are no other enabled plugins in my project. I'm not getting the error when I use the demo project, but when the plugin is in my existing project with all plugins disabled, this crash happens. It seems to have something to do with the larger size of the game project and something failing during the loading process.