Can confirm that this happens on mars too, just myself (hunter) and another hunter were trying to do it fir Last Word. Crystal was immune even after the shield went down. Please Bungie, this is not the kind of thing you need getting to the press.
Dug up an old reddit post from over a year ago. If a titan places a barricade on either plate it will make the crystal on that side immune. BUNGIE fix this garbage its more annoying now with the Last Word quest.