Mixed integer optimization using GA

I am trying to solve a mixed integer optimization using GA. I use linear inequality matrices constraints. when I ran the optimization on matlab I found that the values of the integer variables that can be zero or 1, did not change from value of one. Attached 2 files of mini optimization that I built in order to check the problem. I ran matlab with these two functions, and the optimal fval was 58.5, with value of 1 of the all integer variables (19..27). while by checking the fval (Z) with x(20)=0 and x(11) =0 (other variables are the same as the optimal value). Even though this solution meets all constraints with Z= 53.5. the matlab did not give me that solution.(there are more than one solution that give me 53.5 as Z). I did not know what is the problem. Thanks a lot, Hend