hah! I got it. I was misremembering the ProcMon results when I moved between ProcMon and looking in the Ragnarok install folder. The file it was looking for was not LEVEL.107 but 107.MAP and subsequently 107.UP. These are the file names the Valhalla version uses. I don't know why it randomly wants the different file, but dumping in those two from the Valhalla install seems to make everything work okay. I guess we can call this case closed for now.
Thanks for your help. Knowing it was a missing file issue really helped me know where to look.
Oh color me embarrassed. Those files, along with another pair were included in the rag25 zip, but for whatever reason I'd deleted them, probably because you used to not need any of those .map files back in the day cause it made its own. It's still strange that those few would be required in that version.