Exact same thing happened to me here once. I botched a potential high 1'07" run by missing the last LB. Would've easily been low/mid 1'08" for sure.

Yep, I was just trying for a flap myself. Would've beaten my PR by a full second or more if I didn't choke.
My GV2 NTSC 5lap was just the opposite. I was going for platform jump laps and hit the jump in laps 2, 3, and 4 (and I wasn't yet using NBT on this track, either) but I didn't drive a tight lap 1 at all (13"08), because I didn't think it would turn into a 5lap PR with that lucky PJ streak. Lost an easy 1'00"xx there (and that would have ranked
really high on the Non-NBT chart).
I've also had a couple of last-lap PJ fails at the 5/5 Non-NBT on GV1 NTSC that would have ended in a mid-1'01" time (easily Legend standard)
On PAL, I know I've blown at least one possible Titan 5lap (low 1'08") on CI2 because I bungled the last mud lake boost, after driving four clean laps in the mid 13"xx. PR is still north of 1'09", because getting consistent mud-lake boosts seems to be more of a pain in PAL.
I'm also pretty sure I lost a potential high 1'32" (or at least low 1'33") on BC3 PAL during one race from final-lap choking, after attempting flap PRs.
Every fisherman... and Karter... has their story of "the one that got away"...

SMK sure can try your patience at times... it's one reason why I haven't tried to improve either my NTSC or PAL times in nearly 2 years. Maybe Mr. Ballard can give me motivation to play again...