One all in a race to seven.

I instantly thought that the correct move must be 7/2*. We have a stronger board, builders if they miss/dance, a blot in the opponent's home board if we are hit, and the counterfeit of the two for the blot on our five point. Gnub sees this as a pretty big mistake, preferring 13/8 or 8/4, 8/7 over it.

Am I missing something here? I just don't understand how leaving a shot on 13 or breaking our 8 point could ever be better than the hit in such a spot. On my notebook so may lack the computer power for Gnub to behave properly which may be the explanation - any other ideas anyone?

If you want to play this as a blitz, you must be aware, that you have already 3 men in the rear position. Soon you will run short of ammu, to complete your attack.
If you look at your position as a blocking or priming position, you have already a broken six prime with a hole on third and one and a half prisoners. Red needs desperatly every move a three to stay in the game. Meanwhile you have only to wait for targets to shoot on, threatenend by your prison. If you can hit on your five point, and there is no return, red will be cooked. So, hold your great asset, the broken six prime and wait with your anchor for good things to come. The only winning plan of red then is to scramble home with his stragglers, hoping to win the race. So you don't need your bar point. 13/8 will hold the position and brings another man on the line of scrimmage. XG agrees in XGroller+, so i think, no rollout necessary. This is right for red holding the cube and also a centered.
By the way, XG said if you want to mess up your broken six prime for attacking purposes while holding the bar and not hitting, 7/6, 7/3 is better. That is easy to understand, because you have then three attackers.

1. XG Roller+ 13/8 eq:-0,215
Player : 47,41% (G:13,04% B:0,66%)
Opponent: 52,59% (G:10,37% B:0,37%)

2. XG Roller+ 7/6 7/3 eq:-0,271 (-0,057)
Player : 45,33% (G:13,23% B:0,40%)
Opponent: 54,67% (G:10,89% B:0,41%)

3. XG Roller+ 7/2* eq:-0,284 (-0,069)
Player : 45,64% (G:15,19% B:0,62%)
Opponent: 54,36% (G:14,76% B:0,65%)

Yeah that makes sense - thanks for the great analysis.