Hello Nat,


Do you mean you added a second "constrained_group" block?  
Yes, and sun of occupancies is not 1.
 
This is
incorrect - you should use multiple selections instead:

occupancies {
     constrained_group {
       selection = "(chain A or chain B) and (resseq 105 or resseq
110:112 or resseq 140:143) and altid A"
       selection = "(chain A or chain B) and (resseq 105 or resseq
110:112 or resseq 140:143) and altid B"
     }
}

I think that will force the sum of occupancies to be 1.

Yes, this works fine: occupancies for all alt_A are equal (same for alt_B) and sums are 1.

Any suggestion to add the 20ich waters in this region to the above selection?

Thanks,
Lionel