Mobs equipped with armors or elytra via dispenser won't guarantee 100% dropping such items upon death

Steps to reproduce the issue:

1. Place a Dispenser, put any armor or elytra inside

2. Summon any mob that is able to wear armors near the dispenser (e.g. zombie, skeleton, etc)

3. Activate the dispenser to equip the mob with the armor or elytra

4. Kill it

Expected result:

The mob will 100% drop the equipment given by dispenser

Actual result:

The mob won’t drop the equipment sometimes, or it drops the equipment with a damaged durability

[Note: This may be an old issue, and if earlier reports of this bug exist, please tell me and mark my post as a duplicate]