Hmmm. Deleted the whole smash, restored the backup, copied pasted renamed etc., this time it worked, got a clone with no errors. Dunno what I did different, but I'd rather be lucky than good.
Next step is getting rid of the siren/whistle, looking at the .dsd file I don't see any reference at all to siren/whistle/whatever? I could strip the whole thing down to whatever makes it a static object if necessary, it will never be an actual ship, just static scenery.