I'd already tried exactly that svg four versions ago. The point of the sub-parts was to allow the gates to be positioned separately anywhere in the diagram in a 'straight line' fashion, whilst still retaining the chip body with its ground and vdd connections and preserving the external pin layout. Here is an example of how this can be used for a simple two bit adder:
The chip 'carcasses' look dreadful currently, even without the terminal error on the Vdd; I can't make them look any better. I might decide redo as two sets of parts; one without sub-parts but the correct pin order, another with sub-parts, but the pins not in order. The removes the need for the dog legs and related buses and should look neater. I was hoping to avoid having to work on twelve parts though.
Does the part crash yours though? It does mine when you try to connect the legs to anything; sometimes before that.