My heart doesn't fill in minecraft although my hunger bar is full

My half heart is always missing

i killed myself 2 times.I thought it was fixed but it wasn't 

i used to potion of healing it fixed but temporarly

EDIT:
i opened new world._ i wore boots(netherite) with Depth strider_ it was occurred a bug. However i changed difficulty from normal to peaceful it fix my heart is fill for full after that i again changed difficulty old settings, it occured bug again i have missing half heart then i again i changed difficulty from normal to peaceful it fixed also i took off my boots after that i again changed difficulty old settings. it didnt occure any bug. when i eat something my heart can full