I was trying to dispense armor (iron helmet) to zombies. First worked like a charm. Next never worked. Tried on more than 5 zombies to be sure. Everytime, the item is just spitted out as if the zombie was not here.

The zombie is placed in a minecart on a rail.

Tried to put the dispenser at the zombie head level, at the rail level, tried dropper, tried other wearables, tried tools, tried to restart the game, tried to leave the area, tried going to the nether and back, tried to nametag a zombie.

What I expected to happen was...:

Zombie is equiped with iron helmet

What actually happened was...:
Helmet flies over the zombie head

Steps to Reproduce:
1. Put a zombie inside a minecart.
2. Place a dispenser aimed towards the zombie.
3. Place helmet inside the dispenser.
4. Shoot the item at the zombie.