27 Thunderbolt display wont wake after break on MBP

Hi All and thanks for any help.

Sys:

MacBook Pro (15-inch, Mid 2012)

IOS Yosemite 10.10.3

Display:

27-inch (2560 x 1440)

NVIDIA GeForce GT 650M 512 MB graphics

I have a 27inch Thunderbolt Display connected to my MacBook Pro (15-inch, Mid 2012). When I plug in the thunderbolt cable to my MBP, it detects the TB display and works perfectly. When I take a 10 min break, and come back to a sleeping MBP, both screens are black. Then, I hit the mouse/keyboard to wake up the computer., it completely ignores the TB display and shows a single screen on the MBP. In fact it seems like it tries to connect to the display at first (it doesn't show the dock or top bar) but then it ignores it completely and brings back the dock and main top nav to the MBP.

The thunderbolt screen remains black at all times and the only way around this is to unplug and plug back the thunderbolt cable and then it works. Of course this is not a good solution not only because it's not a good idea to plug and unplug over and over again, but I also have portables and USB devices conected to the back at all times.

Anyway, any help would be greatly appreciated it.

Thank you!