Diagnosis
You want to assign periodicity &V2& to period &V1&. However, period &V1&is already included in a period chain with period &V4&; periodicity &V3&is already assigned to period &V4&. Therefore, periodicity &V3& isalready implicitly assigned to period &V1&.

Procedure
You can assign periodicity &V2& to a different period, or you can assigna different period to periodicity &V3&.