ID 313056 - Nuke Studio doesn't playback 4K DPX at 25fps on some machines when monitor out is active

Problem summary
Nuke Studio doesn't playback 4K DPX at 25fps on some machines when monitor out is active

Customer reported version
nuke.10.0v2

Customer reported platform
windows7

Steps to reproduce

1) Open Nuke Studio

2) Import a 4k DPX sequence and add it to the timeline

3) Play back the sequence, it will play back at 25fps

4) Open the Monitor Out window and select DeckLink 4K Extreme with at 2160p25

5) Play back the sequence, it will now bounce between 21-23 fps, not 25fps

Reproduced by support
Tested on 3 different Foundry machines, these steps only work on on of them

This problem has been reproduced on:
Nuke 11.0v2 - Windows 7 - CentOS 7
Nuke 11.0v1 - Windows 7
Nuke 10.5v5 - Windows 7
Nuke 10.5v1 - Windows 7
Nuke 10.0v6 - Windows 7
Nuke 10.0v1 - Windows 7
Nuke 9.0v9 - Windows 7
Nuke 9.0v1 - Windows 7

Mac not tested due to hardware limitations

Earliest version tested
Nuke 9.0v1 as Studio was not available before

Expected behaviour
For Nuke Studio to continue to playback at the same framerate

Actual behaviour
The FPS dropped from 25 to 21-23 when monitor out was enabled