Version: 1.10.2-2.0.6.156
Replicability: I am able to successfully reproduce this bug.
Steps to produce:

1. Create an Energy Core, in my case it's a tier 7 and I have not tried this with other tiers.
2. Place a block under the Energy Core, in my case it was a Wyvern Energy Relay Crystal. And I was able to reproduce the bug using a Draconic Energy Relay Crystal.
3. Get a Staff of Power. In my case this was the one I used:

• Enchantments/Upgrades: http://i.imgur.com/Cda1QX0.png
• Profile: http://i.imgur.com/DTld0Di.png

4. Destroy the Energy Relay Crystal [or chosen block] underneath so that it will destroy the ACTIVE Tier 7 Energy Core.

I have not tested this bug in single player but only in multiplayer. If you require further information you can find me on lolnet by the name of WintrAU

This may be fixed in the latest version.