2010 models: usually just a bad C9560. Samsung VRAM is sometimes bad. Also MUX issues are common with "analog" distortion on LCD but no crashing and locking up.
2011 models: Good luck finding real NEW GPUs, let me know if you can find them. Don't even think about upgrading it is useless and just another risk factor. VRAM on these is never bad, if any issue a reflow/reball should fix it. Also these have issues with vias in the board, about 10% of the boards have internal problems like that.
2012 models: GPU issues on these are not the GPU and not the VRAM, I think the issue is in the board vias like the 2011.
As you see it is just a complete cluster fuck.
2011 models: Good luck finding real NEW GPUs, let me know if you can find them. Don't even think about upgrading it is useless and just another risk factor. VRAM on these is never bad, if any issue a reflow/reball should fix it. Also these have issues with vias in the board, about 10% of the boards have internal problems like that.
2012 models: GPU issues on these are not the GPU and not the VRAM, I think the issue is in the board vias like the 2011.
As you see it is just a complete cluster fuck.