1.16.5 [1.16.5] Problem with rendering item on a tile_entity

[Mr_Kubbe]

Hello!
I was working on my custom campfire tile, and suddenly got a problem. The problem is with the rendering of the item in the campfire inventory. The TileEntityRenderer says that the inventory is empty, witch is strange cause the existing logic for the cooking food works normally. Additionally, when i leave and then rejoin the world, the item renders, but the inventory is not saved really well (could be caused because of the not finished save logic).
I would be really thankful if you could help me with this problem!

Link to the entire code; https://pastebin.com/tHZ9snN7

I'm sorry if i had presented the post not well organized. It is my first post on this forum, and I'm not sure how to a well structured post. Additionally I would give my apologies for the not well structured code, I had tried to fix it in multiple ways (unsuccessfully). Feel free to criticize the code with good criticism. I am open for improvements.

[Mr_Kubbe]

Man I can offer anyone 20$, that helps me understanding and fixing the problem.