Storage Class issues while code generation

I have two subsystem which have the same buisness logic and hence I have made them re-usable with one function name in RTW tab. The two subsystems have separate output names on root layer but inside the names of outpts are same in both subsystem.As soon as I make the storage class of their outputs as ExportedGlobal I get an error while code generation as the two subsystem should be exactly identical to generate one re-usable function. This error doesnt come if the storage class is set to auto and also the code is properly generated with only one function.

The error pops up when I set its storage class to some value like ExportedGLobal or Global.

Please help.