a!forEach Not Working When Items Comes from Local Variable

I have a local variable that holds an array. When I pass this local variable to a a!forEach items, it does not loop. When I take the array value and paste it directly into items, it works. Why is it not working when I pass in the array from the local variable?

a!localVariables(
  local!groups: {
    cons!AX_ALL_USERS,
    cons!AX_MECHANICS,
    cons!AX_REGISTRARS,
    cons!AX_SUPERVISORS,
    cons!AX_ADMINISTRATORS_POINTER
  },
  {
    a!sectionLayout(
      label: "Groups for " & loggedInUser(),
      contents: {
        a!gridField(
          label: "",
          labelPosition: "ABOVE",
          data: todatasubset(a!forEach(
            /* WORKS */
            items: {
              cons!AX_ALL_USERS,
              cons!AX_MECHANICS,
              cons!AX_REGISTRARS,
              cons!AX_SUPERVISORS,
              cons!AX_ADMINISTRATORS_POINTER
            },
            /* DOES NOT WORK */
            /*items: local!groups,*/
            expression: {
              {
                groupName: group(fv!item, "groupName"),
                isMember: a!isUserMemberOfGroup(loggedInUser(), fv!item)
              }
            }
          ), fv!pagingInfo),
          columns: {
            a!gridColumn(label: "Group Name", value: fv!row.groupName.),
            a!gridColumn(label: "Member?", value: fv!row.isMember)
          },
          validations: {}
        )
      }
    )
  }
)