nonvul V vul, sit south, and hold:

S: A Q J 9 4 3
H: K 2
D: Q 10 2
C: 10 6

Partner open 2C (strong), East bid 2NT ( he said it's H and D), the following bidding is like this:

N---E---S---W
2C--2NT-X--3D
3H--/---3S--/
4C--/---4H--/
5C--/---5S--/
/--/

5S-1. 6C is cold. What's the problem of the bidding?

Here is North's hand:

S: void
H: 10 5 3
D: A K 5
C: A K Q J 9 5 4