NPC Characters causing unwanted physics impulse

I have a rolling ball game where you control a rolling ball that is simulating physics at all times. I have some human characters that run around, i notice that if they run close to the ball, i get a bit of an unwanted physics impulse from them that pushes the ball a little bit. it’s not like the ball is getting totally blocked, it can still push through and make contact with the npc character, but the force is quite obvious and it is very annoying. I have made sure that there are no overlaps taking place and there are no force components in either the ball or the human npcs. the impulse only occurs when the npcs are running. it does not happen if they are standing still. what could it be?