As i was playing single player while using a cheat added elytra it would not activate while jumping off hills.

I experimented alittle with it to see if i could repeat the bug and could not.

I then later ocured the same bug while playing creative mode after i tried to "shift delete" the inventory. And the elytra would not be deleted. It then proceded to lose it's flying ability.

The elytra was still an item i could throw away and pick up. But it would not activate.

I hope this was helpfull