I have this bug regulary
I have soldiers that are free now and can be sent to the strategic operation
I click on that operation and see a list of all my soldiers but their names are grey in this list and I cannot select any of them from the list becouse of it.
I make a save, exit the game, start it again, load the save, do the same things again - the list is white this time, so I can select soldiers now and send them.
So I have to do this save\restart\load trick almost every time when I want to send soldiers to strategic operation.