Operating system: Darwin-18.7.0-x86_64-i386-64bit 64 Bits
Graphics card: AMD Radeon Pro 560X OpenGL Engine ATI Technologies Inc. 4.1 ATI-2.11.20
Broken: version: 2.81 (sub 15), branch: master, commit date: 2019-10-14 16:46, hash: rB879d269e8769
Short description of error
There's no step by step to reproduce this. The only thing I know is: when working with reference pictures sometimes they go missing from the viewport. When they do, I can't select anything anymore directly on the viewport. I can select on the viewport. If I try to sculpt I get results, if I enter edit mode the mesh wires don't show and I can't move it by clicking.
If I save, quit Blender and reopen everything goes back to normal. So it doesn't corrupt the file.
Exact steps for others to reproduce the error
Work with reference images on the viewport and... wait for the error?