I got this error recently too, and managed to reduce the test case. It’s not a steady-state error. Macros like ForEach, ForLoop, etc, seem to get corrupted when a downstream node has an error, and the only way to fix the upstream macros is to recreate them. Deleting the node that introduced the error does not fix the problem!
The problem node for me is SpawnActor with a runtime-specified actor class, and the actor being spawned has ‘exposed on spawn’ parameters. It seems the way this problem is exposed (for me) is to corrupt all upstream macros.