If you use visual inheritance, especially with frames, for some unknown reason the IDE decides to randomly update the .fmx file. It changes inherited to object. You may get the following error:

The solution is to close the project, open the affected .fmx file in a different text editor, and change object back to inherited. For example, from:
object ArticlesView: TArticlesView
Size.Width = 209.000000000000000000
Size.Height = 443.000000000000000000
object Scroller: TVertScrollBox
Align = Client
Margins.Top = 8.000000000000000000
Size.Width = 209.000000000000000000
Size.Height = 435.000000000000000000
Size.PlatformDefault = False
TabOrder = 0
Viewport.Width = 209.000000000000000000
Viewport.Height = 435.000000000000000000
end
end
to:
inherited ArticlesView: TArticlesView
Size.Width = 209.000000000000000000
Size.Height = 443.000000000000000000
object Scroller: TVertScrollBox
Align = Client
Margins.Top = 8.000000000000000000
Size.Width = 209.000000000000000000
Size.Height = 435.000000000000000000
Size.PlatformDefault = False
TabOrder = 0
Viewport.Width = 209.000000000000000000
Viewport.Height = 435.000000000000000000
end
end
I hope this tip helps.