i have made my own pumpkin, with seeds and stem but the model for the stem when bent towards pumpkin doesn't work - it shows magenta/black cube.
in code i did everything like vanilla pumpkin so the problem must be with blockstate or model
Blockstate:
{
"variants": {
"age=0,facing=up": { "model": "archeology:emerald_pumpkin_stem_growth0" },
"age=1,facing=up": { "model": "archeology:emerald_pumpkin_stem_growth1" },
"age=2,facing=up": { "model": "arche