NPCs can't pass gates when they are going to their upkeep location. They stuck at the frame of gate and they don't even move until you push them. I am not sure if this is a bug but its annoying. Is there a way to make NPCs can understand gates?

What type of gate is it, and what size is it ?

Size and type doesn't matter. The problem is pathfinding AI chooses the shortest way and can't understand there is a gate frame.