There is an issue with some of the older interiors such as that for the F7.
As an FYI when asking about an asset always give the name and the KUID number. This helps us confirm if the problem is specific to that model or the assets in general. The issue we have with Trainz in general is the shear number of assets with some with similar names. So "the F7" means nothing just as the boxcar, house, etc.