im having delays and lag but not drops on fps kinda

im playing the better mc modpack and im having delays such as blocks i break reappear and mobs freeze and unfreeze despite me playing singleplayer i have 16 gigs of ram with allocated to the game and i have amd ryzen 5500 with rtx4060 i play on 100 fps on avg but they these issues happen so often like every 15 sec or so