Car's going 90% like a dream but, under heavy acceleration, 2nd to 3rd (I think) is odd.
It feels as if it gets into 3rd but then seems to "hunt" as if not knowing whether it should remain in 3rd or drop back to 2nd. Ease back on the pedal and it establishes 3rd and all continues fine.
I fear this may be serious but, as all else is so good, will be tempted to leave well alone and drive sedately!