shield bug, what is it?

[derfinsterling]

The workaround makes the game playable again, but there are tactical subtleties which are invalidated by the workaround.

Sorry, but I wanted to add that while this certainly is a bug, it doesn't make the game "unplayable".
CTD make a game unplayable, corrupted savegame files do, but not a thing like this.
Yes, you ever have to use a mod or live with it (adjusting your tactics accordingly), but it's not unplayable.