Okay, I found a copy. *ahem*
This game uses
mapper 64, which is the RAMBO-1 mapper.
New information about this mapper has come to light, specifically with regards to its IRQ behaviour. Full details are in another thread on this forum:
viewtopic.php?f=3&t=10439The scanline counter being "off by one" near the bottom of the screen (see screenshot), where the clock is, could be explained by the aforementioned thread. But the garbled graphics seem to imply a possibly-related-yet-different problem (my guess is CHR page switching which doesn't work correctly/isn't emulated correctly). Whether that's related to IRQ timing or not is unknown, I would have to investigate further. It could be just as likely that Nestopia's mapper 64 emulation isn't accurate given the small number of games that use said mapper.
If this turns out to be a Nestopia issue, there is an official board to report them (not here), but it's unlikely anything will be done about it since the official versions of Nestopia are no longer maintained. There are a couple third-party maintainers of it however.
This doesn't appear to be a ROM problem because the game actually renders graphics correctly in VirtuaNES and FCEUX... sort of. You can't really play the game at that point, but at least things visually seem to be right. See screenshots. Don't ask me how
this guy was able to play the game, since I can't get any joypad input to do jack squat once the game starts.