Yeah, this. It's gotta better in the last 3-4 years since he's became truely elite, but before when he was just an one win a year guy and not a star he was a big time bottler. But it still flairs up. When was it, 2016? When he threw away the Fedex Cup in the Tour Championship and Rory won it?
Yeah he's gotten a bit better at closing but if we look at his career at majors, he's let so many of them slip away.
2010 US Open: Had a three-shot lead after 54 holes and proceeded to implode on Sunday by shooting an 82. Also, considering the final winner finished at E for the tourney, DJ could've shot a +5 in round 4 and the victory still would've been his.
2010 PGA Championship: Had the 71-hole lead and got penalized for grounding his club in a "bunker" which cost him like 3 extra strokes on that hole and ultimately the tourney. Many ppl thought he got robbed on this one by a bogus ruling, and almost 9 years later, I still feel for DJ on this one
2011 Open Championship: Was within a shot of the lead after round 3, but shot a dismal +2 in the final round to lose to Darren Clarke who was legit like 45
2015 US Open: Within a shot of the lead on hole 72 with a 12 ft eagle putt to beat Spieth. He completely blew it by three-putting and essentially handed the trophy to Jordan
2016 US Open: FINALLY broke through. He also had to overcome some bs rule official from what I remember too
2018 US Open: Tore up Shinnecock Hills for 3/4 rounds, but in the one round where he didn't play well he completely collapsed and fell back to the field with a +7 in the third round. He was -4 in his other 3 rounds which meant he could've shot 4-over in round 3 and he still would've beat Koepka by a stroke
As you mentioned above, DJ also fell apart in the final round of the Tour Championship, losing it to Rory, despite only needing like a top-10 finish in the tourney to win his maiden FEC.
If DJ had snagged these chances, he'd already have more majors than Phil and more US Open's than Tiger (!!), while still only being 34. DJ would also be the heavy favorite in the "greatest post-Tiger player" discussion as well.