Regression: Document type editor does not show moving a field to another column

I work with archetype 1.07.01, based on cms 7.8.1.
Go to the document type editor, create a new document type (based on the basedocument super type). Choose the 2 column layout. Create a new field, say of type String. Move that field to the right column using the triangle (>). Try to move it back to the left column with the <-triangle. This fails: the field remains in the right column.
Clicking "done" fixes this: the field is shown in the correct column now. There is no trace in the log.