Let me explain my situation. I have some Document Libaries that derives from some content type some columns.
In some of these columns I have (by mistake) add two times the same columns with different names.
When I tried to delete it from PowerShell I user the command
SPList list = Web.Lists["NAME"]; SPContentType ct = list.ContentTypes["CTNAME"]; ct.FieldLinks.Delete("Descrizione Pratica"); ct.Update();
I believed that these will destroy only the column for the given content type but what I found now is what you can see in the picture:
I tried in many way to add the column back to my lists:
Adding and removing it from Site Content Type
Adding and removing it from List Content Type
Adding and removing it from Fields of the list
But the list consider the field horribly wrong: I cannot insert data in that column, I can't se data stored... It's like the column does not exist..
Thank you very much!