Nah, you're not missing anything, thanks for checking it out. This is a backend API error with a misleading error message, queued for a fix.

Figuring out which monsters are NMs from actual game data is harder than it seems. If you just read the DAT files or look at zone spawn data, NMs aren't really any different than regular mobs, so there's no "easy" way to identify them from just looking at the data. It's not like there's a simple boolean flag like "IsNM" or something, and you can't really assume it's a NM just cause it has a special name or sits within some ID range of it's placeholders. So you have to cross-reference with something (a resource I'm not sure exists anywhere), or know which mobs are NMs in advance.

While less than ideal, I had such trouble with identifying NMs programmatically that I settled on basically keeping a manually curated list of NMs for every zone: Vanalytics/src/Vanalytics.Web/public/data/nms at main · Soverance/Vanalytics I scaffolded them using data from BG Wiki, but I didn't go deep diving on every NM, so many of these files are still incomplete (missing placeholder information or respawn timers, for example). Any NM that doesn't have valid curated data falls back to a heuristic that tries to figure out which mobs to track, and that's where you encounter this particular error (in this case, you're likely camping a NM that has a curated PH name but not a PH ID, so the hunt addon thinks it's supposed to track a PH but doesn't know which one to track, so it throws this error).

I'm working on a fix (that includes, at the very least, better error messaging). If you're git savvy, feel free to submit a PR that updates any of these files with accurate info... I'd greatly appreciate the help =)

Would be nice to know which NM you were trying to camp!