Shouldn't you also change the brick's client and stack BL ID?
for(%i=Brickgroup_47704.getCount();%i>=0;%i--){%b=Brickgroup_47704.getObject(%i);%c=findClientByBL_ID(48284);Brickgroup_48284.add(%b);%b.client=%c;%b.stackBL_ID=%c.BL_ID;}
There's really no reason to call
findClientByBL_ID every iteration of that loop.
%c=findClientByBL_ID(48284);while(BrickGroup_47704.getCount()>0){BrickGroup_48284.add(%b=BrickGroup_47704.getObject(0));%b.client=%c;%b.stackBL_ID=%c.BL_ID;}
Also, with Xalos' and Jes' code, you're actually going to want to make the for statement
for(%i=BrickGroup_47704.getCount()-1;%i>=0;%i--) because setting
%i to the size of the group will cause the first iteration to error.