Hey minegunvany,
UATHelper: Packaging (Windows (64-bit)): UE4Editor-Cmd: [2017.04.18-10.24.46:917][ 0]LogInit:Display: LogProperty:Error: UStructProperty::Serialize Loading: Property 'StructProperty /Game/UI/Item.Item_C:item'. Unknown structure.
UATHelper: Packaging (Windows (64-bit)): UE4Editor-Cmd: [2017.04.18-10.24.46:918][ 0]LogInit:Display: LogProperty:Error: UStructProperty::Serialize Loading: Property 'StructProperty /Game/UI/Item.Item_C:items.items'. Unknown structure.
UATHelper: Packaging (Windows (64-bit)): UE4Editor-Cmd: [2017.04.18-10.24.46:918][ 0]LogInit:Display: LogProperty:Error: UStructProperty::Serialize Loading: Property 'StructProperty /Game/UI/Item.Item_C:abilities.abilities'. Unknown structure.
UATHelper: Packaging (Windows (64-bit)): UE4Editor-Cmd: [2017.04.18-10.24.46:919][ 0]LogInit:Display: LogProperty:Error: UStructProperty::Serialize Loading: Property 'StructProperty /Game/UI/lockedItem.lockedItem_C:item'. Unknown structure.
UATHelper: Packaging (Windows (64-bit)): UE4Editor-Cmd: [2017.04.18-10.24.46:920][ 0]LogInit:Display: LogProperty:Error: UStructProperty::Serialize Loading: Property 'StructProperty /Game/UI/lockedItem.lockedItem_C:items.items'. Unknown structure.
UATHelper: Packaging (Windows (64-bit)): UE4Editor-Cmd: [2017.04.18-10.24.46:921][ 0]LogInit:Display: LogProperty:Error: UStructProperty::Serialize Loading: Property 'StructProperty /Game/UI/lockedItem.lockedItem_C:abilities.abilities'. Unknown structure.
Those are the errors I’m seeing in your log. I recommend making sure that you have properly saved all of those structs, and also that none of them have been removed or have extraneous references. Take a look at the thread linked below for an example of how one user solved the same error:
I’d also highly recommend performing a search for your error in our documentation. It will bring up any references to this on the Forums, Answerhub, Wiki, etc so you can easily search to see if other users have experienced similar errors and give their suggestions a try.
Have a great day