Document Type Editor Link Compound field pointing to the wrong type

We are experiencing a weird behavior in the Document Type editor.

We are trying to add the standard Link compound type to allow users to link document types within a new document type. When we go to add the field to the document type itself, instead of the Link field we get one of our custom compound types.

What could cause this to happen? I am not seeing anything in our namespace cnd file referencing hippo:mirror and we do not have a type matching Link within our namespace. Also, if we create a document type under another namespace, the Link Compound seems to function as expected.

Check if you have right prototype in your document template, might be you have/had a different type defined with same name (this is just a guess, I would expect some errors/validation to be triggered in such a case)

also: does this happen with all documents or only old ones?

@mkjp2011 can you some picture of what is your problem?