Currently, the support for Visio shapes is in an early stage. Several cells and functions are not yet supported. When a shapes contains such an unsupported feature, yEd checks whether it can be safely ignored or not. In the latter case, yEd discards the original shape and shows an error symbol instead, a red 'x' in a rounded rectangle.
One of the most noticeable missing features is support for 1-D shapes.
