Sprite prefab instances only render when camera is selected?

I have a 2D scene mostly comprised of a grid of tiles. These tiles each represent one pixel of a source image, and so are instances of a sprite prefab.

Everything ran smoothly until early this morning, when the behavior of the scene suddenly changed for the worse. Now, the prefab instances do not seem to want to render in the game view unless one of the cameras is selected in the hierarchy. Depending on the size of the game view, sometimes the sprites can be made to appear by pausing/unpausing the simulation.

It should be noted that any instances of the prefab that are created in the scene prior to running all show up fine, it's only instances that are created with the Instantiate method that seem to behave this way.

I've been beating my head against this for hours to no avail. Changing the sprite's sorting layer or layer order does nothing. I had thought this might be an issue of the multiple cameras having conflicting Depth variables, but this turned out to not be the case. Setting the scene view to 3D, I can see the sprite instances fine in the scene, but again the game view refuses to (consistently) render them unless a camera is selected.

Any help on this would be appreciated.