It is my understading that you are using Assignment blocks and the element of input port has a value of 2 but this value is out of permissible range which is (0-1) in your case. It seems that you have selected Index mode: zero-based and provided Idx1 input which contain index values based one-based indexing.
Set the Index mode: one-based in the block parameter of the Assignment block in Simulink to resolve the issue.
