Here's the "6th printing" errata updates. But see Pukunui's clarification below!
Fighter - Spells Known of 1st-Level and Higher (p. 75). The final sentence ends as follows: “… unless you’re replacing the spell you gained at 3rd, 8th, 14th, or 20th level from any school of magic”.
Warlock - Spell Slots (p. 107). In the example, thunderwave has been replaced by witch bolt.
Wizard - Minor Conjuration (p. 116). The conjured object also disappears if it deals any damage.
Multiclassing - Spells Known and Prepared (p. 164). A new paragraph appears at the end of this subsection: “If a cantrip of yours increases in power at higher levels, the increase is based on your character level, not your level in a particular class”.
Feats - Alert (p. 165). The third benefit now reads as follows: “Other creatures don’t gain advantage on attack rolls against you as a result of being unseen by you”.
Adventuring - High Jump (p. 182). After applying your Strength modifier, a high jump is a minimum of 0 feet.
Darkvision (p. 185). The definition of darkvision here now matches the definition everywhere else in the game.
Resting (p. 186). The text clarifies that any creature, not just adventurers, can take a short or long rest.
Short Rest (p. 186). After applying your Constitution modifier to a Hit Die roll, you regain a minimum of 0 hit points.
Long Rest (p. 186). The first sentence of the rule now reads, “A long rest is a period of extended downtime, at least 8 hours long, during which a character sleeps for at least 6 hours and performs no more than 2 hours of light activity, such as reading, talking, eating, or standing watch.” In addition, you regain at least one Hit Die when you finish a long rest. (Note this change was not marked out as 6th printing.)
Spells- Moonbeam (p. 261). The words “up to” now appear in “move the beam up to 60 feet in any direction”.
Prismatic Wall (p. 269). The spell no longer refers to a rod of cancellation, and the text clarifies that dispel magic works only against the violet layer.
True Resurrection (p. 284). There’s a new sentence at the end of the second paragraph: “If the creature was undead, it is restored to its non-undead form”.