The glint disappears whenver you throw your enchanted item on the ground (as an item entity)
the glint also does not render in some cases such as villagers, witches and foxes holding an item or armor stands wearing cenchanted armor pieces that causes the glint to may disappear in some angles.
Linked issues
is duplicated by 15
10 more links
Happens to me both on fast and fancy options. Probably a rendering issue.