SIMULINK: upperBound​Size.isUnk​nown()

am trying to simulate a feedback loop in simulink involving PID controllers and optimization algorithm. I have individual bits of code that run well, but when i put them together I'm getting errors. The errors do not pin-point at anything, but I have traced it to use of MUX in the code. I'm attaching the pic of the MUX causing the error, the output of max should be 3 but its 1 instead and the rest of matlab function gives error like

upperBoundSize.isUnknown()

Simulink does not have enough information to determine output sizes for this block. If you think the errors below are inaccurate, try specifying types for the block inputs and/or sizes for the block outputs.

Index expression out of bounds. Attempted to access element 3. The valid range is 1-1.

Undefined function or variable 'TyR'. The first assignment to a local variable determines its class.

This code works well in other place.