Hello, when I want to transfer the steel solid to another project with Copy-Paste from the File in a structure whose first floor is reinforced concrete and the upper floor is steel (the project I want to transfer is the top floor of the same reinforced concrete 3-storey version), I get an error as in the picture. Tried on two different computers, same error. * It is a computer with SSD hard drive and 16 GB ram. I wish everyone good work.