Temporary Image ghosting on iMac 5k display

When I quit out of a program, there's a faint ghosting of the window that remains typically around the edge of the screen. I also see it on the menu bar when I shut down or restart. I'm working in 'dark mode' for most everything, the ghosted pages usually have a white or lighter colored background. It doesn't seem to matter which program I'm using. InDesign, Bridge, Text Edit. It's slight, but noticeable.

This goes away when I zap the PRAM or NVRAM. It just started happening recently and occurs even if I only have that window open for 10 to 20 minutes, not long enough for 'burn in' to occur. Te only thing that has changed around the time this started happening is that I replaced my USB Mouse with a wireless trackpad. I can't imagine that has anything to do with it, but it oddly started happening right around that time.

Mojave 10.14.5

Mac (Retina 5K, 27-inch, Late 2015)

4 GHz Intel Core i7

64 GB 1867 MHz DDR3

AMD Radeon R9 M395X 4 GB