Exporting buggy model to a fresh file

[William Gray]

I have a file which appears very slow when working on the model. It contains a lot of surplus information which is proving awkward to delete. I would like to export my model to a clean template file. In both files, I've selected all layers, switched them to visible and unlocked them all. I've unlocked everything and set the renovation filters to Show All. I've then put a heavy marquee around the part of the model I want to export and selected all. When I try to paste the model into the new file I am told that the renovation filters don't match. I've checked to ensure that the filter is set to Show All in each file. When I paste the model into the new file several items are missing eg roofs. Can anyone help?