Photoshop interminable when copying layers

I'm running Photoshop CC 2018 on Windows 10.  The machine is a Dell 7710 mobile workstation with 32 GB RAM, an Intel on board video card, an Nvidia Quadro M5000 GPU w/ 8 GB VRAM, and 3 fast SSDs.  Preferences are set up to allow 25,000 MB (85%) of RAM, Graphics Processor, 8 Cache Levels, 1028K tile size (Huge Pixel Dimensions).

I'm working on a file that is large but not huge (8.69 GB). I'm running into a situation where copying a layer or a selection from a layer is interminable.  Example: I selected the pupil of an eye and used ^J to put the selection on a separate layer.  It took fully 10 minutes to copy that selection.  I run into the same situation if I try to duplicate a layer into another document.  However, I am not experiencing any kind of lag in my brush or other type of memory related problem.

I have worked on files as large as 35 GB w/o experiencing this problem.

Does anyone have any idea what might be going on?