Disparity between AdvanceMap colors and in-game colors

[TaviTurnip]

Hey guys. I'll keep the details strict and to the point:

• This is a binary FireRed hack. I've been using AM 1.92. There is nothing previously wrong with the hack or its tilesetting or colors, and this issue doesn't impact any existing maps. It's isolated to this one situation.
• This has involved overwriting map tileset 16 (from a supposed list of unused/dummy tilesets 16, 24, 33, 35, 39, 55 and 56) and the actual tiles themselves seem to work great.
• Yes I have absolutely crushed the "Write palette changes to ROM" button repeatedly. Lots of people with a similar issue have also clarified that they've done this step.
• This button doesn't seem to exist in AM 1.95, and in general using 1.95's interface to do tilesetting stuff seems way more difficult, but I digress.
• I have tried doing palettes first, then tiles + block information, and vice versa. Order doesn't seem to change anything.
• I've heavily referenced [this thread] for all the pertinent info for adding tilesets, but the answers scattered throughout haven't helped.

As a test I've been trying to import a map from Pokémon Vega wholesale. When imported strictly as a map, it looks like this:

Spoiler: Base map using default map palettes

When the proper modified tileset from Vega is inserted, along with its palettes, it looks like this (which is the correct outcome):

Spoiler: Snowy map! (Ignore the garbage tiles, those are from tileset 2)

This is the part where a bunch of fledgling hackers get stumped, and I've been no different :x When loading up the game to check the palettes, the result is very different. Since the connected maps don't have changed tilesets/palettes yet as I've been working on getting this to work in the first place, first the colors are taking from the current map's palettes:

Spoiler: This is roughly what it looks like before palettes are changed anyways

But when you reload the map from the menu or by going in-and-out of a building...

Spoiler: COMPLETELY unrelated colors that do not pertain to any palette on any tileset

Any buildings from tileset 1 are completely black silhouettes, which seems to pertain to palettes 10-12 specifically, but everything else like grass, paths/roads, and the like, are all gross and yellowy, and absolutely no palettes anywhere use these colors, making it seem like it's reading garbage data for them. Closing AM 1.92 and opening it back up continues to show the desired colors in the map editor. Opening it in 1.95 (or attempting this process from scratch in 1.95) shows it with the same yellow colors. This makes me think that AM thinks it's changing the palette but the pointers in the tile data in the ROM aren't actually being updated, or these palette datas are being stored somewhere without the map data being updated to reflect it. I can't seem to find the offsets for things like map tile data in HMA either, so it's become kind of a dead end for me.

Any thoughts?