imac 5k mission control lag?

What is the deal with "mission control lag" on the new iMac 5k's?

HERE'S MY SETUP.

iMac 5K (late 2014 configuration: 2015 build)

• 4.0GHz Quad-core Intel Core i7, Turbo Boost up to 4.4GHz
• 8GB 1600MHz DDR3 SDRAM - 2x4GB

  upgrade to 32GB from OWC.

• 512GB Flash Storage
• AMD Radeon R9 M295X 4GB GDDR5
• LG WH16NS40: USB 3.0 (BluRay R/W);
• WD MyBook for MAC: USB 3.0 (External HD 3TB);
• Audio-engine 2+: USB 3.0;
• ASUS PB278Q - true 8bit color (2x) /display port;
• Logitech Performance MX mouse;
• Kinesis Freestyle 2 for Mac keyboard;
• Rode Microphone Podcaster w/desk stand;
• Fujitsu Scansnap S1500M scanner;
• Anker 3.0 USB Hub;
  • AH121 USB 3.0 7-Port Hub with 36W Power Adapter

  • 12V 3A High-Capacity Power Supply and VIA VL812 Chipset