So sorry about your colony losses folks…
When robbing starts in spite of reduced entrances, in addition to a screen I drape a damp beach towel over the front face of the hive. Basically stick it under a brick on top and hang it down longways and kind of turned back around the front corners, so the one small entrance has another detour to it. Your bees will have some trouble finding their way in too but not as much as the robbers - the dampness helps buffer the scent and give the guards an extra minute to fend em off.