Dual monitor strangeness

[MacInWin]

I have a new MBP, mid-2015 rMBP 15". I also have a Thunderbolt monitor that worked great with my old early 2011 17" MBP. But with the new one, if I let the laptop sleep, sometimes when it wakes it doesn't wake the Thunderbolt. It's random, seemingly. When it happens, System Preferences/Display doesn't even show the Thunderbolt. And the only way to "fix" it is to reboot the MBP. My old MBP 17" never had this problem, when it woke up, it brought the TB display with it.

So, is there a setting I'm missing somewhere? Both were running 10.11.5, so it's not the OS itself, it is either a system setting or something different in the hardware.

What I want is for the two to sleep at the same time and wake up when the MBP wakes, every time.

 

[Raz0rEdge]

When I wanted to get a second monitor for my iMac, I ran across many people have this particular problem and the bulk of the blame fell on the TB/Mini DisplayPort cable being used. The monitor didn't seem to matter much in this case if I recall. I ended up going with the cable that seemed to work best for people and I've had no issues with my second monitor waking up once the iMac work up.

The cable I went with is: http://www.amazon.com/dp/B004065DAC/?tag=macforums0e4-20

 

[MacInWin]

Ashwin, thanks for that. I'll look into a cable, but what's curious is that this is the original Apple cable with combination power/TB connectors and it works well with the 17" but not the 15". It could be bad, I suppose, but it's strange that it works with one and not the other.