Progression Bug - Kabala Clan Relic not dropping

In act 2, whilst completing the side quest 'Ancient Vows', I went about obtaining the Kabala and Sun Clan relics required for the Valley of the Giants Buff. I was quickly able to obtain the Clan relic in Mastadon badlands, but did not find the 2nd relic in my first pass through of Keth. I traveled to the Valley of Giants, placed the Sun Clan relic from Mastodon, and returned to Keth to obtain the 2nd required Relic.

Unfortunately, after 5 consecutive attempts at obtaining the 2nd relic from Keth, clearing all 3 sections of the Keth map (Entrance area, Lost City 1, Lost City 2) of all enemies, I am still unable to obtain the 2nd relic piece. I have tried with another player in a party with me, I have tried resetting and running the area fresh, and gained 10 levels trying to find the 2nd relic for the buff from the Valley of the Giants.

I am unclear whether my premature placement of the first relic at the Valley of the Giants is what ultimately halted my progression and made it impossible to find the 2nd relic piece, or whether this is a known (or unknown) bug impeding my completion of the side quest. Either way, please advise any potential fix to this issue, or how I can manage to obtain the Valley of Giants buff some other way. Thank you for your consideration.

Same here, I go back every so often to try and get it, after trying over 10 map clears of the different areas there (I'm now lvl 90) I must have cleared 10-15 maps.

Seemingly the same is true for Act III Apex of Filth mushroom drops for Bubbling Respite, I can't complete that either.