[thie]

I am wondering why the new and supposedly improved GIB version 31 would pass on
this and this
hand where I thought the bidding was clearly forcing. The results were obviously disastrous.

[manudude03]

On the first board, your 4NT bid showed both minors. I don't know why it didn't bid one of them, but I assume it was something to do with simulation.
As for the second, a takeout double isn't forcing per se, more like partner is just expected to remove it. I guess it simulated pass based on the possibility of hitting a 4-3 fit which doesn't rate to play well with the bad breaks.

[iandayre]

I don't know what you were doing on #1, but I certainly don't understand GIB's pass. The second one really needs to be fixed. Hey GIB, takeout doubles are meant to be TAKEN OUT!!

[thie]

I also noticed that 4 nt showed the minors. One player was in 6♠ though after the same initial bidding. In his case 4nt was explained as blackwood for spades (which actually makes more sense to me. Why not reserve 5♣ over 4♠ to show the minors?)
So something must have changed (it was an instant tournament so 6♠ was played with an earlier GIB version). Most players passed 4♠ which is rather too pessimistic for my taste seeing as how little you need pard to have for a decent small slam at the least. Still I don't quite understand the pass, as I certainly did not promise a heart stopper anywhere 4 nt might easily be 4 down from scratch, you would expect that to be factored into the simulation.

And I guess I don't like the simulation then on the second board
Passing in this situation without much defensive values / trump values is just about a deadly sin in my book.