State Tree invalid transition index - what does this mean and how does it happen?

I’m working on a (relatively) simple AI StateTree where the main tree just has:

Root
├─► Patrol
└─► Chase

Where:

  • when the player is closer than 400 units thePatrol state can be entered
  • when the player is further than 400 units the Chase state can be entered

I’m not 100% sure why i’m getting this “Invalid transition index 2 for state tree” or what it actually means so i’m struggling to figure out what could be causing it?

The resulting behaviour is that the enemy attacks then just stands there


debugger

Could anyone help or shed some light? I’m on 5.5.4 if that helps!

Here’s some screenshots of the subtrees:


main tree


patrol SubTree


chase SubTree