Copper Golems can’t pathfind through thin blocks (such as fences, chains, and end rods) even though it fits and can be pushed through.
To recreate; embox a Copper Golem with the thin blocks and place a Copper Chest outside for the golem to pathfind to. Make sure there are gaps in the hitbox of the fencing, yet no full air block way out, as well as no way for the golem to jump out over the blocks. Now observe how the golem stays put and stares at the copper chest trying to pathfind to it. To confirm that the golem would fit the gaps you can push it out with your hitbox.
it works as intended