Ghosts of objects remain on screen after delete

While not critical, does anyone know why I have a visual 'ghosts' left on screen after I have deleted objects or portions of text. In the example screenshot, the middle column has been deleted, but an artifact remains on screen until I switch pages or cause something to redraw that part of the screen. Not every case, and I haven't tested enough to figure out what circumstances might be consistent.

Model Name: iMac

  Model Identifier: iMac17,1

  Processor Name: Intel Core i5

  Processor Speed: 3.2 GHz

  Number of Processors: 1

  Total Number of Cores: 4

  L2 Cache (per Core): 256 KB

  L3 Cache: 6 MB

  Memory: 28 GB

  Boot ROM Version: IM171.0110.B00

AMD Radeon R9 M380:

  Chipset Model: AMD Radeon R9 M380

  Type: GPU

  Bus: PCIe

  PCIe Lane Width: x16

  VRAM (Total): 2048 MB

  Vendor: ATI (0x1002)

  Device ID: 0x6640

  Revision ID: 0x0080

  ROM Revision: 113-C6005R-800

  EFI Driver Version: 01.00.800

  Metal: Supported

  Displays:

iMac:

  Display Type: Built-In Retina LCD

  Resolution: 5120 x 2880 Retina

  Pixel Depth: 30-Bit Color (ARGB2101010)

  Main Display: Yes

  Mirror: Off

  Online: Yes

  Automatically Adjust Brightness: Yes

  Connection Type: DisplayPort