Now these aren't always so much "errors" as they are editorial changes, modifications that Phoenix made. We all know that he took the EU exclusive quests (from White Dwarf Magazines, Dave Morris' novels, the Marvel Winter Special, those fanzines like Drago Brasil and Adventures Unlimited, and the unfinished sample quest from the back of the Adventure Design Kit as well as of course the official Dark Company multi-quest from 'Advanced Quest" edition as well as Against the Ogre Horde and Wizards of Morcar expansions that were not released in the US) and converted them to NA rules. He also know that in Elf Quest Pack (mage of the mirror) he famously replaced the Quest 1 reward of the Elven Chainmail and replaced it with the (previously unused, and with no card) Elven Bracers artifact. The 2023 remake (thanks to early unboxings this month!) of EQP showed us that the Elven Bracers were re-introduced as a treasure found IN Quest 1, but anyway...
In the process of comparing the 1992 EQP to the new remake I found a few more discrepancies or editorial changes in Phoenix's version:
Quest 7:
Near the middle there one of those goblins should actually be an Orc.
Quest 8:
Yes, note D refers to a "bag" of Heroic Brew... this oddity was present in the original! (another place where Phoenix made an editorial change to "bottle").
Phoenix puts in a Mummy on the right edge that should be a skeleton.
In Kellar's Keep there is a bad guy who can reduce your Mind Points to zero. In the original it actually says that the Hero who has this happen to him is dead "forever" unless there is an Elixir of Life to save him. Phoenix changed it to be like Return of the Witch Lord, where a zero mind point hero is simply "unconscious" for the rest of the quest (which of course is how ROTWL originally was, unlike EQP and BQP where they introduce the "going into shock" rule).
I also noted that there are "too many doors" called for in several of the Frozen Horror quests, but this is an error in the original, not a flub by Phoenix. Just as the original Dark Company calls for too many pieces of furniture in places (which doesn't really impact gameplay, just ideal aesthetics), so too BQP called for approximately 7 more open doors than come with the game system (re-use them or mime opening the closed doors, 3d print extras, etc).