3D geometric when adding materials

Hi all i am new working in 3D geometric inside comsol . when i bulit 3 Block in diffrent Width and heigth but in same depth and when i add fourth one in diffrent depth i found all of 3 blocks before devided after add fourth one . how can i solve this problem . please see the picture 1 the geometric and picture two the same geometric when i try to add the materials thank you