Data Gen - Block Model from JSON template throws error

I am trying to generate my block models with Data Generators which I incounter this error.

It's easy to spot why this error occurs ("block/minecraft:sand", ':' triggers the error) but I don't understand where this error could come from by looking at my code.

Since I have a few variants of the same block, I've replicated Minecraft's way by defining a template JSON for my variant and simply have my block use it as a parent and add a texture.

Heres what I have:

    private void generateSiltBlockFenceGateFromTemplate(SiltFenceGateBlock gate) {
        String texture = Objects.requireNonNull(gate.getParentBlock().getRegistryName()).toString();

        getVariantBuilder(gate).forAllStatesExcept(state -> {
                String base = "silt_fence_gate" + (state.get(OPEN) ? "_open_" : "_close_") + state.get(AbstractSiltBarrierBlock.LAYER);
                if (state.get(IN_WALL)) base = base + "_in_wall"; 
                // <base> would look like "silt_fence_gate_close_1"

                ModelBuilder<?> model = models()
                        .withExistingParent(texture + "_" + base, modLoc("block/template_" + base))
                        .texture("texture", mcLoc("block/" + texture)) // <--- stacktrace points here
                        .element().end();

                int rotation = (int) state.get(HORIZONTAL_FACING).getHorizontalAngle();
                return ConfiguredModel.builder().modelFile(model).uvLock(true).rotationY(rotation).build();
            },
            WATERLOGGED
        );
    }

I've also tried to feed it a texture as a string directly but to no avail:

                        .texture("texture", "block/" + texture) // <--- stacktrace points here

What I expect is sand_silt_fence_gate_close_1.json:

{
  "parent": "siltsand:block/template_silt_fence_gate_close_1"
  "textures": {
  	"texture": "sand"
  }
}

Here's my template JSON: template_silt_fence_gate_close_1.json:

{
  "parent": "block/block",
  "textures": {
    "particle": "#texture"
  },
  "elements": [
    {
      "from": [ 14, 0, 7 ],
      "to": [ 16, 1, 9 ],
      "faces": {
        "north": { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "east":  { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "south": { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "west":  { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "up":    { "uv": [ 0, 0, 2, 2 ], "texture": "#texture" }
      }
    },
    {
      "from": [ 0, 0, 7 ],
      "to": [ 2, 1, 9 ],
      "faces": {
        "north": { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "east":  { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "south": { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "west":  { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "up":    { "uv": [ 0, 0, 2, 2 ], "texture": "#texture" }
      }
    },
    {
      "from": [ 2, -1, 7 ],
      "to": [ 14, 0, 9 ],
      "faces": {
        "up":    { "uv": [ 0, 0, 12, 2 ], "texture": "#texture" },
        "north": { "uv": [ 0, 0, 12, 1 ], "texture": "#texture" },
        "south": { "uv": [ 0, 0, 12, 1 ], "texture": "#texture" },
        "west":  { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "east":  { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" }
      }
    },
    {
      "from": [ 10, -7, 7 ],
      "to": [ 14, -6, 9 ],
      "faces": {
        "up":    { "uv": [ 0, 0, 4, 2 ], "texture": "#texture" },
        "north": { "uv": [ 0, 0, 4, 1 ], "texture": "#texture" },
        "south": { "uv": [ 0, 0, 4, 1 ], "texture": "#texture" },
        "west":  { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "east":  { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" }
      }
    },
    {
      "from": [ 2, -7, 7 ],
      "to": [ 6, -6, 9 ],
      "faces": {
        "up":    { "uv": [ 0, 0, 4, 2 ], "texture": "#texture" },
        "north": { "uv": [ 0, 0, 4, 1 ], "texture": "#texture" },
        "south": { "uv": [ 0, 0, 4, 1 ], "texture": "#texture" },
        "west":  { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" },
        "east":  { "uv": [ 0, 0, 2, 1 ], "texture": "#texture" }
      }
    }
  ]
}

I have read that maybe this might be caused by invalid JSON but that has been checked too.

Any idea why this happens? 

PS: I am new to Data Gens so it is very likely that I using the builder wrong.

Edited September 24, 20214 yr by than00ber1
added further explanation