Champion still not taking damage after 3 indestructible buffs down

This has now happened to me twice on same run, so can 100% confirm this is a bug. I have removed all 3 of the indestructible buffs by dexing specials, and still all hits afterwards are still doing 0 damange. Using stealth spidey and have 2 active buffs up (Burden of Might and Unblockable), in case that makes a difference. I spent many revives to get him down and am out a ton of units. I submitted a ticket but wanted to share if others are having similar issues. I recommend not attempting for now.