19 down: Ubiquitous John a young herbivore (3)

18 across: Tail-ender (Indian mid-off) caught by famous 19-down (doe) misled into ferocious drive (5, 8)

These go a young herbivore = doe = Doe = ubiquitous John and tail-ender (Indian mid-off) caught by famous doe misled into = l Indian – ian caught by Bambi tion = blind ambition = ferocious drive.

There’s one relatively minor issue: a doe is a female herbivore, not necessarily a young one.

But as Caitlin pointed out, the actual error comes from famous doe = Bambi. Unbeknownst to a lot of us, including DA it seems, Bambi was male! Hence, he was never a doe, although once upon a time he was young.

16 across: Horror film keeping man in reserve before rotten finale (3, 4)
The explanation goes: keeping man in reserve before rotten finale = keeping he in tome before n = the omen = horror film.

In that, you probably noticed something questionable: reserve = tome.

No need to question it, though, it’s an error, and a very understandable one that DA himself described making in his own words:

Meanwhile 16A, the clue for THE OMEN, holds a blunder. At first draft, I’d used the word ‘book’ in the clue, which hampered surface sense. As proof phase, I thought ‘reserve’ read far better, however ‘reserve’ may signal BOOK, but never TOME. A sloppy conflation. My apologies. Feel free to file under Bullshit.

If I had my time over, my salvaged clue would read: Horror film keeping bloke in work until production’s end (3,4). But that raven has flown.

Are editorial cutbacks the cause?:

15 across: Argentine plainsman fully backing emperor (7)
Both Wikipedia and the Spanish Royal Academy confirm it: a llanero is from Colombia or Venezuela, not Argentina.

10 across: Cruise line largely ill-advised to strike malign… container (8, 3)
A pandora’s box is 7’1, 3 in length, and not 8, 3.

28 across: Engrossed in computer, private nerd makes Sudoku (5, 6)
I was considering granting this to DA on metaphorical grounds, but then I thought against it: a magic square is something that a Sudoku puzzle most definitely is not.

26 across: Row starting early for depleted Foursome? (4)
Ian makes a good suggestion: this clue should read row ending early for depleted Foursome so that the solution is row ending early = riot ending early = trio = depleted Foursome.

As the clue stands in the crossword, it’s a clear error.

6 down, 21 across: Spooner’s out of depression with 13-down (bombproof) snack (5, 5)
The answer works without bombproof: Spooner’s out of depression = Spooner’s from pit = pomme frite = snack.

That’s just as well because the reference to 13-down, the solution to which is bombproof, should actually be a reference to 15-down, the solution to which is deep fryer.

15 down: Soulful cleric employed in Maccas, we hear (4, 5)
Quite a good clue: soulful cleric we hear = deep friar we hear = deep fryer = employed in Maccas.

The problem that you might have noticed with my rearranging of the clue: we hear should be at the start of the clue, not the end.

3 down: She follows win, or upset (9)
Almost a good clue: win, or upset = success or upset = successor upset = she follows.

That upset shouldn’t be there, as DA makes clear from the comments to the crossword’s list of confusions:

The word ‘upset’ in 3D is the crossword-equivalent of a sponge left behind in a surgery patient.

Ian is quite right, as are AL and RB. The word should have been removed before sewing up the final copy.

Why ‘upset’ was there in the first place was originally I’d tried to make an ellipsis with 4D. I’d been playing with the idea of win [SUCCESS] and upset [reverse one part of the TREE wordplay].

But that ploy fizzled, and I’d been flogging the […] tactic anyhow in recent weeks, so I re-sealed both clues and left the damn wettex behind! Am I upset? Of course. It’s shoddy. Almost suit-worthy.

Thanks for the wake-up. I’ll strive to…um…’expunge’ any further cases of malpractice in this puzzle’s successors. Best, DA

2 down: Rival forged audio (4)

It’s surprising mistakes like these don’t happen more often, but a mistake it is. The clue should be forged rival audio so that the explanation becomes: rival audio = foe audio = faux = forged.

16 down: Twice your old yacht regulars crowed about being stranded? (4-4)

Here, twice your old yacht regulars = twice ye ah = yeah-yeah = crowed about being stranded.

The direct clue is too oblique for my tastes (and the answer not funny enough for that to be excused), but more problematically the ye has been misused.

Ye is a subject pronoun for the second-person plural, the Middle English equivalent of yous or you all in contemporary times, and definitely not a possessive pronoun, which your in modern day English is.

(And the ye in ye olde expressions is also not a standard feature of ye olde English, but it is quite a strange grammatical element that is not equivalent to an article, like the for instance. Instead, it seems to act merely as a marker that harks back to ye olde days).

Anyway, another spotting has been made of that most fugitive of creatures, a DA error.

15 across: Prize awarded in or about the late 1930s (9)

The clue is supposed to work prize awarded in = edwardian = about the late 1930s.

I’m willing to concede the American spelling of prize instead of the Australian prise, but in no way, shape or form are the late 1930s Edwardian.

Clearly a slip up, and one that happily happens only rarely.

6 across: 8, 27 and 64 die (5)

I’m calling it as DA’s second error in a calendar month! Here, 8, 27 and 64 = cubes = die, which is incorrect because die is the singular form of dice, meaning that the clue should have been 8, 27 and 64 dice.

It’s too bad, because it would have been a candidate for DA Gold otherwise (I like maths, and I have a sneaking suspicion that mathematically-minded people are the best at cryptics).

Update: This is not actually an error. AL set me on the right course.

As AL pointed out, I am in error here, not DA.

I read the clue as suggested above, 8, 27 and 64 = cubes = die, which would have been a DA error.

The alternative is to read it as 8, 27 = cubes = 64 die, which is not a DA error.