This happenend to us when changing parameters in the Family Types dialogue.
- not able to change a Revit parameter from Type to Instance (or otherwise)
- not able to change a value of a Revit parameter eg width = 600 to width = 400
We changed the "UniformatClassifications.txt" to our own classification.
We developed our own Revit library and added directly the Assembly code in it for all objects.
Problem occurs when
- Re-install of Revit and forgot to change the "UniformatClassifications.txt" file, OR
- Use of other Revit objects referencing the wrong assembly code, OR
- Use of another Revit project specific "UniformatClassifications.txt" file
Select the Assembly Code in the Family Types dialogue and
- delete the value
- change the value by pressing on the ... button to a good Assembly code