There is an issue with carpet-extra and hopperoptimizations. Carpet-extra uses isValidInvStack to make hoppers not insert items when there is already 1 item in the same slot of the autocrafting dropper. Therefore it will return false, when the stack is valid, but the slot already has an item. The correct solution would be to implement SidedInventory::canInsertInvStack instead.

SidedInventories usually do not have that property, that you suddenly cannot insert stuff. Even shulkerboxes are SidedInventories. Also the naming of the method implies that you are using it incorrectly, also how it is used now does e.g. beacons return true without checking if the slot is occupied already.

HopperOptimisation has patched this now.