What’s wrong with this auction from an OK Bridge board? South was dealing with no one vulnerable:

                        NORTH
                       ♠️ K Q 4 2
                       ♥️ K J
                       ♦️ A 9 6 5
                       ♣️ A 10 3

WEST                                     EAST
♠️ J 10 9 3                             ♠️ 7 5
♥️ 10 8 3 2                            ♥️ Q 9 6 5
♦️ Q J 2                                ♦️ 8 4 3
♣️ Q J                                   ♣️ 8 7 6 5


                       SOUTH
                      ♠️ A 8 6
                      ♥️ A 7 4
                      ♦️ K 10 7
                      ♣️ K 9 4 2

The bidding proceeded as follows:

South         West          North           East
1♣️            Pass          1♠️            Pass
1NT•           Pass         4NT••          Pass
6NT•••         All Pass

• Almost certainly showing 12-14 high-card points
•• Asking partner to bid 6NT with maximum
••• Blamelessly bidding 6NT with 14 HCP

Opening lead: ♣️Q

Even with the most favorable opening lead possible, North-South made only 10 tricks, with losers in spades, hearts and diamonds.

NoTrump bidding can be strictly mathematical, and the numbers here don’t add up to a slam. With 17 HCP, North should have known the pair held a maximum 31, at least one short of aspiring for 12 tricks. Once South rebids 1NT, North should simply bid 3NT to end the auction.

What’s wrong with South’s bidding on this hand? West was dealing, with no one vulnerable:

     SOUTH
     ♠️ K
     ♥️ A 10 6 3
     ♦️ 5 4 3
     ♣️ K Q J 5 2

The bidding proceeded as follows:

West            North           East          South
2♦️               DBL            Pass          3♥️
All Pass

South jumped to 3♥️ opposite partner’s double, but that shows 9-11 HCP. With an opening hand, South should bid 4♥️.