Error message when trying to add topicrefs to 1st level of ditamap

[TechWright]

Hi!

I have a ditamap which I have opened after rearranging my xml folder and file hierarchy. The ditamap doesn't allow to insert new topicrefs as siblings of other 1st level xml files or a s child of the ditamap itself.

Only an error message appears saying "Element definition doesn't exist or element is not valid at this location".

I am able to place xml files on the fist level by adding them to lower levels first and then moving them up in the hierarchy.

Anybody has any idea what causes this or what have I done to break my dear ditamap? (Other than reorganised my file locations.)

[TechWright]

Additional information: After I've inserted the xmls on lower levels and moved them up to the 1st level, then it is possible to insert a child but still NOT sibling xmls.