Textures not wrapping onto item models

[octa]

 

 

You can see the handle and part of the top of the axe are flat. This is happening with all except for two of the tools I've made, and I can't discern any difference between the broken ones and the ones that work correctly.
 

 

Here is the texture im using in the above example: https://github.com/eddie1101/PortalTest/blob/master/src/main/resources/assets/basicportals/textures/item/item_void_axe.png 
Here is the model json: 

{
  "parent": "item/handheld",
  "textures": {
    "layer0": "basicportals:item/item_void_axe"
  }
}

 

Here is the rest of the project: https://github.com/eddie1101/PortalTest

 

Please let me know why this is happening.
Thanks.

Edited January 30, 2021 by octa

[Draco18s]

Because some of the pixels are transparent, but not completely transparent.

So the game thinks you should be able to see through the item.

 

[octa]

Can you tell me how you're viewing the image?
When I view it in gimp it looks pretty clean:
 

Edit: Using Gimp's threshold alpha tool worked wonders. Thanks for the help.

Edited January 30, 2021 by octa

[Draco18s]

I used Curves to show the pixels with boosted values.

 

Here's the histogram, you can see some tiny bars in the lower left.

 

In pulling the anchor on the curves panel over I can make those values more apparent.