Loyal Customer Buff bugged for myself. Only receiving 12% increased dmg and healing, should be 18%, had my renown bugged and reset too low for several weeks and now missing an extra 2 buff levels (3% each or 6% total) from my Liberation of Undermine buff, the quests are not available on the npc.
This issue has been present for myself since the first renown rollback fix about 2-3 months ago now. (I beleive I was able before they fixed back the missing 9 renown levels for those of us affected by it to turn in 1 or both of the first 2 reputation quests but they rewarded 0% extra damage/healing; both displayed on buff and tested in-game, so this may be the issue).