Protected Hexes Question

[HMCS Rosthern]

To view protected hexes one goes view->shade->protected hexes.

if all of the reinforcements have been received in the area of the protected hexes, will this shading no longer show?

The reason why I am asking is that in a game in progress one set of protected hexes is no longer showing shaded, but when I go to the start of the same scenario (i.e., new scenario) those protected hexes are shaded.

Or is this a bug?