I try to make custom models for items, using sprites in it (in realistic fern model, for example), but in third person view both textures of sprite appear at the same time, which makes it glitchy-looking.

Steps to reproduce:
I variant:
1. /summon Enderman ~ ~ ~

{carried:38s,carriedData:1,NoAI:1b}

2. /gamemode 3 to take a closer look on the model.
II variant:
1. Create a resourcepack.
2. Change any item model, so it will have this part of code (taken from vanilla sunflower model):
"textures": {
"back": "blocks/double_plant_sunflower_back",
"front": "blocks/double_plant_sunflower_front"
},
"elements": [
{
"from": [ 9.6, 15, 1 ],
"to": [ 9.6, 30, 15 ],
"rotation":

{ "origin": [ 8, 24, 8 ], "axis": "z", "angle": 22.5, "rescale": false }

,
"shade": false,
"faces": {
"west":

{ "uv": [ 0, 0, 16, 16 ], "texture": "#back" }

,
"east":

{ "uv": [ 0, 0, 16, 16 ], "texture": "#front" }

}
}
]
3. Get the item with changed model in your hand.
4. Press F5.