Factorio Forums

When you hit 'R' over belt piece to rotate it items on the belt remain there. But when you drop belt piece over via building (left-click), resources from belt go to your inventory if dropped piece has different orientation. IMO placing differently rotated item over existing one should work same as rotating original item, and it it works this way for inserters (placing same type of inserter rotated differently does not get item from its hand to your inventory). It's minor issue but it happens frequently when you update your belt network to red or blue and miss direction somewhere.