In my case root motion of the skeletal mesh inside the capsule caused that issue. The feets of my character stick out of the capsule component while running (see attatched image). My guess is that root motion adds force while moving which causes the bumping. Thats what I did:
Go to edit->project settings->collision and add a new object channel (name it so you can identify the object type, in my case I named it ‘Zombie’). After that you go to your mesh settings inside the blueprint of the AI. Click on the mesh component. Now go to details (right side of the screen on default) and look for ‘Collision’. Make sure you set ‘Collision Preset’ to Custom. Change the object type to your newly created object type (in my case ‘Zombie’). Below the object you should find the new collision response (‘Zombie’). Click on the checkbox for ignore on that item ('Zombies). This makes sure that the skeletal mesh of the same type won’t collide and the bumping should go away.
Cheers,
J.
