SAP Message UCF1003 - Entries for the allocation are contradictory

Diagnosis
You want to run an allocation. However, the sender objects could not befully depleted because your specifications concerning the distributionare contradictory.
Example of contradictory specifications:
Sender A distributes 100% to receiver B, but sender B distributes 100%to receiver A.

System Response
The allocation cannot be executed. Data will not be modified.

Procedure
Define the method without contradictory specifications fordistribution.