We have create a workflow with table decision to set different value depends selction code, but variable taht we used to catch value is not fill , it remains always null

Someone it's already happens, we are tested different combination using same datatype , or using different datatype, set initial value or not , but we have not found as manage this occourence.
It' s my opinion id a bug of version and i've already open an incient , but maybe someone have found a trick
Andrea