{solved} uv_1 malfunctions in Edit and Texture Paint Mode

Hello. I'm having a weird problem with Blender than I can't find anything online about. Basically, I'm trying to make the hat from the "favorite clothes" scene in the Sonic OVA. I have my uv_0 map finished and it is not causing any problems, as you can see in the picture below.

imgur.com/a/XPVyOLE

However, I went to duplicate it so the game could find/use a uv_1 map when the situation called for one, only for Blender to create several faces for vertices which were not connected. None of the faces appear to have any existing edges associated with them or generated to accompany them. This results in the texture getting scrambled and severely distorted, with overlaps everywhere, when it is translated to the 3D model using the uv_1 map. See the image below for an example of what I'm talking about:

imgur.com/a/LWgU1WV

Oddly enough, the problem only seems to exist in Edit Mode and Texture Paint Mode. In Object Mode and Sculpt Mode, the excess faces do not appear in the uv_1 map and the 3D model looks the same whether it is uv_0 or uv_1 mapped. In the below image is the uv_1 map on the 3D model in Object Mode-- as you can see, the model looks the same as the uv_0 mapped one.

imgur.com/a/jLEaVxF

Things that I have tried thus far:

• Re-unwrapping the model. I have done this quite a few times and it does not appear to make a difference in the outcomes. After re-unwrapping, the uv_0 map still duplicates incorrectly. After re-unwrapping, the uv_1 map retains the old geometry and pastes the new geometry on top of everything in the active image. Rarely this causes lag, but it never alleviates the distortion.
• Re-stitch the UV maps. This is another thing I've tried many times. Depending on the settings, this either does nothing or creates extra edges and faces that distort and scramble the texture's appearance on the 3D model.
• Delete and replace the uv_1 map.
• • There are no online tutorials that I could find explaining how to empty a UV map or remove geometry from it without disconnecting and deleting it completely from the 3D model. Most guides simply say something to the effect of "try not to use more than one UV map," which is solid advice that doesn't help me at all since (from what I can tell) the Sims 4 expects a uv_0 and uv_1 map to be present on all CAS items.
  • Using the "Paste UVs" option results in nothing being pasted, and "Copy UVs" doesn't appear to do anything either.
  • To my knowledge, you cannot import UV maps from PNGs or SVGs
  • Trying to get around the lack of deletion options by merging all the vertices to produce something that is close enough to an empty UV map for me to work with results in almost all of the edges, but almost none of the vertices or faces, being deleted.
  • The Rip Region tool in the UV Editor shows an error message when I attempt to use it on the uv_1 map, regardless of where I click and what is selected.
  • Resetting the UV maps is a remarkably bad idea. The outcome is basically always either a crash or severely distorted textures.

• Reset the rig. I made sure my "geom-skin" modifier had all the right settings then used the widget to reset it. This seemed to fix the uv_1 map in Object Mode and Sculpt Mode, but the problem persisted in Edit Mode and Texture Paint Mode. I also checked for typos in the vertex groups, and found none.
• Checked for available updates for Blender and my OS. Everything is up-to-date as far as I know.

I am currently running Blender Version 3.6.1 on an Intel macOS Pro 2019 Ventura 13.4.1 with Retina display. My Blender file is linked here: file

Also, I am very, very new to using Blender so please explain everything like I'm five. Thank you!