Why I get different result in a same Maximize Solveblock?

I used MC15M030 to solving an optimitization problem, and I defined ALL >= 0, all the variable large or equal to zero.

I have used 4 methods to do it in a same Maximize Solveblock, but I have got 3 different result.

Look at the pictures below:

the result of (1) and (2) are same and right.

(3) and (4) are different and wrong.

How to explain this puzzle?