Sometimes Eyes-of-Ender fill portal frames but don't activate the portal!

What I expected to happen was the portal to be activated as soon as all the Eyes-of-Ender were placed!

What actually happened was that when I placed all of the Eyes-of-Ender, it only activated the portal within a few tries, so only creative mode was possible to get past it!

3 to Reproduce this bug are:
1. Open a world in Creative Mode
2. Build an Ender Portal
3. Put in the Eyes-of-Ender, sometimes it won't activate the portal!