Thank you, everyone. Due to this thread, we've confirmed that the issue that was occurring in the Fall of Truth and many old raids has been conclusively fixed.
We've also uncovered and successfully reproduced a different issue with one specific raid, The Reaver's Fate, where a Jewel of Fortune or a Loot Bonus Weekend can cause you to get no treasure. This only affects that raid, and no others. This issue will be fixed in Update 18.