There is no expletive to express this.
Up until now, I have been working with the smaller GJD files that get installed to the hard drive, but I couldn’t find a delta frame there that had a palette change. So I went for a biggy: the INTRO.GJD file on disc one. It’s good I did, because I’ve discovered that the bit that was easy, the extraction from the GJD file, doesn’t work properly. It gets about two into it (out of a couple of dozen), then falls over.
Still, I’ve already learnt / re-learnt quite a lot since I did that bit, so it might be obvious…