blocks requiring support drop when filling with air

Blocks needing support like torches, levers, pressureplates, ladders, signs, flowers wich are placed on the east, south, or up side will drop when filling both the supported and the supporting block with air

 

This happends with both "/fill X Y Z x y z air" and with the loading of air blocks from structureblocks

 

strangely it does not happens with redstone powder, repeaters, comparators, sugarcanes and scaffoldings

not all blocks were tested