User &1 is already part of planning round &2/&3 - No transfer in phase 1

What causes this issue?

User &SYST-MSGV1& is already part of planning round &SYST-MSGV2&/
&SYST-MSGV3& and the planning round for both users is still in initial
planning phase. Therefore a transfer of the planning phase is identical
to assigning the objects of user &SYST-MSGV4& to user &SYST-MSGV1& .

System Response

The transfer can't be done out of Express Planning.

How to fix this error?

Use the functionality for object assignment to do the transfer. As long
as the SAP delivered stabdard object service is used this can be done
with transaction <DS:TRAN.FPB_MAINTAIN_PERS_M>FPB_MAINTAIN_PERS_M</>
using planning dialog DIA_CO_CCA_PL.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.