furnace on the left (LP) delivers coal only to the output slot. the furnace on the right (basic BC) delivers only to the correct fuel slot (drops all further items it tries to insert).
edit: replacing the chassi with a basic pipe has the same behavior - no fuel inserting to fuel slot on the bottom.

Caused by the new ISidedInventory from minecraft not handled by BC.

this is a problem that only lp has -- the gold pipe on the right sinks correctly, the lp pipe on the left fails.

Should be fixed now.