After partner opened 2NT, holding 4=4=5=0, the perfect Stayman shape, my response was to raise any response to game, as an 8-card fit is guaranteed. The best contract was 3NT, which could be made, despite my ♣ void, because opener had 4 ♣ with stopper which I couldn't ask for. I was afraid of opening lacking ♣ stopper for 3NT so I didn't take it into consideration.
Board 18, South, 4♠x by North, -2, -12.25 IMP
I held a 17 HCP balanced hand, and my partner held a ♠ bust with no strength. I thought that their 3NT was not makeable due to me having 17 HCP balanced, but my partner thought that they would make 3NT because he had no values so he escaped to 4♠, and used a line of play for 50% success but failed. Most of the field were at 3♠ or 2♠ making 10 tricks, while no opponents at other tables bid 3NT.
I did not understand why the my action was bad.
For board 23, why was 3NT better than 5♦ even when I had a void, and a fit was guaranteed? How could we prevent bad 3NT if we didn't have ♣ stopper?
For board 18, whose fault is it? My fault doubling 3NT or my partner's fault escaping to 4♠?