Well, I don't want the zombies to spawn with any states applied. It's not the cause since it happens with and without. It also haopens without VisuStella, so it's not that either.
Viewing post in How to make these patterns?
I looked at your screenshots and I see you do have an enemies array setup for the map.
Highlighted is the default enemies which I see you have configured. On my end I have also setup region enemies without modifying the code:
Enemies do spawn normally in which I get two slimes.
The code error comes from using the spawn enemy function which has a different line up on my end.
Are you using the latest version of the plugin? I did a series of rapid updates recently.