This deal is from a duplicate at Cheadle in May.
Blocked suits cause many problems. Sometimes you appear to have enough tricks, but can't get at them all, other times there are different problems.
On this deal the diamonds were blocked, with only one entry to the South hand. All declarers played in spades or notrump from the North hand on the lead of the jack of hearts. Those in notrump could unblock the diamonds, cross to table with the spade ace and discard the losing clubs on the diamonds and then play the spade suit in the percentage way by taking the finesse, making twelve tricks. Those in spades could not do this as the fourth diamond would have been ruffed. So they cashed the spade king and crossed to the spade ace, hoping that three rounds of diamonds would stand up and then to play the fourth diamond while the defence got a ruff or not depending on which defender had the third trump. When the queen of spades dropped and the hand with four diamonds also had three spades they were somewhat lucky to make thirteen tricks and beat the declarers in notrump.