Scrambled screen when going out of sleep

Question

With my 2011 MBP, when connected to my external screen I always encounter an issue when waking up from sleep mode, if the lid was closed (and only if lid is closed from what my tests show).
To summarize:

• MBP + External screen + Lid closed
  Wake-up with scrambled external screen and black MBP screen. MBP frozen.
• MBP + External screen + Lid not closed
  Wake-up normally from sleep mode.
• MBP without external screen (lid closed or not)
  Wake-up normally from sleep mode.

Do you have any idea of what could cause this and how I could fix the issue?

Here is how my external screen looks like after a wake-up in the first case:

I've seen this issue but it's for older version of MBP and my system is up to date regarding the Software Update option.

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Edit: Last EFI update installed yesterday seems to have fixed the issue!

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Last update:

Several years without any issue and then, recently, having really serious issues appearing (MBP freezing or rebooting (console showing gpuRestart crash logs)), I went to the Apple Store.

They changed the GPU (hence the full motherboard). This was free because of an extended repair program for this very specific problem. See details here. Program ends in Feb 2016, so hurry up in case you have the same issue!