Secondary Display not waking after screen sleep

Currently i am running into an issue with external displays (projectors)

I am looking at setting up a lab environment at the moment to try and replicate the problem,

but thought id mention what i know so far and see if anyone has any comments to add.

Secondary Screen not waking after screen sleep signal sent.

Symptoms

Issue can be manually recreated by connecting external projector in known problem locations and causing the screen to sleep by pressing ctl+shift+eject to sleep the display, once it has slept waking it by providing an input recreated the problem.

Lectern Macs are locking up when their display is put to sleep (typically due to inactivity) and they are connected to the external projector display,

External display does not show the machine waking again, but the primary inbuilt display does at least show its previous screen.

Other Observations and Tests

Reproducible on several iMacs 21.5" late 2013 models running OS X 10.9.5 and a MacBook Air mid 2013 model running OS X 10.10.2,

issue only appears to only occur connected to projector locations,

Unfortunately i don't have the model of the projectors just yet but they are different brands.

they are connected using Apple Display port to VGA adaptors.

unplugging the Apple display port and reconnecting it will reinitiate the second screens display,

while the display is not waking the Mac appears to recognise the display is connected,

however the Windowserver process is not redrawing the secondary display.

the following log was captured during the process of recreating the problem on an iMac

I have annotated physical actions taken relative to the logs in bold

Forced Sleep of displays with Ctrl+Shift+Eject keyboard input

Main, Active, on-line, enabled, built-in, boot, OpenGL-accel, Vendor 610, Model a012, S/N 0, Unit 2, Rotation 0

UUID 0x2838c3dda39478c14a5e57649bbc5643, ColorProfile { 2, "iMac"}

texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT

off-line, enabled, OpenGL-accel, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 3, Rotation 0

UUID 0xffffffffffffffffffffffffffffffff

texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT

off-line, enabled, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 1, Rotation 0

UUID 0xffffffffffffffffffffffffffffffff

off-line, enabled, OpenGL-accel, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 0, Rotation 0

UUID 0xffffffffffffffffffffffffffffffff, ColorProfile { 3, "Display"}

texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT

Main, Active, on-line, enabled, built-in, boot, OpenGL-accel, Vendor 610, Model a012, S/N 0, Unit 2, Rotation 0

UUID 0x2838c3dda39478c14a5e57649bbc5643, ColorProfile { 2, "iMac"}

texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT

off-line, enabled, OpenGL-accel, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 3, Rotation 0

UUID 0xffffffffffffffffffffffffffffffff

texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT

off-line, enabled, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 1, Rotation 0

UUID 0xffffffffffffffffffffffffffffffff

off-line, enabled, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 0, Rotation 0

UUID 0xffffffffffffffffffffffffffffffff, ColorProfile { 3, "Display"}

Display port cable unplugged and replugged due to machine being slow.

Main, Active, on-line, enabled, built-in, boot, OpenGL-accel, Vendor 610, Model a012, S/N 0, Unit 2, Rotation 0

UUID 0x2838c3dda39478c14a5e57649bbc5643, ColorProfile { 2, "iMac"}

texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT

off-line, enabled, OpenGL-accel, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 3, Rotation 0

UUID 0xffffffffffffffffffffffffffffffff

texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT

off-line, enabled, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 1, Rotation 0

UUID 0xffffffffffffffffffffffffffffffff

Active, on-line, enabled, Vendor 756e6b6e, Model 717, S/N 0, Unit 0, Rotation 0

UUID 0x8d79cbc9a4ecdde112fc91ba625b13c2, ColorProfile { 3, "Display"}

Main, Active, on-line, enabled, built-in, boot, OpenGL-accel, Vendor 610, Model a012, S/N 0, Unit 2, Rotation 0

UUID 0x2838c3dda39478c14a5e57649bbc5643, ColorProfile { 2, "iMac"}

texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT

off-line, enabled, OpenGL-accel, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 3, Rotation 0

UUID 0xffffffffffffffffffffffffffffffff

texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT

off-line, enabled, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 1, Rotation 0

UUID 0xffffffffffffffffffffffffffffffff

Active, on-line, enabled, Vendor 756e6b6e, Model 717, S/N 0, Unit 0, Rotation 0

UUID 0x8d79cbc9a4ecdde112fc91ba625b13c2, ColorProfile { 3, "Display"}

texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT

Things are normal again.