It's hard to debug anything without having the project at hand.
As you describe it and from what I can see on the screenshots, my guess is that newly spawned slimes are somehow different from the first one. In "On start of layout" you set the slime state to "walk" which does work for the first slime that's already there but every slime spawned after will not have the state set to "walk", so perhaps you should take this out of "On start of layout" and put it into the "On slime created" trigger. Maybe that's the issue?