No resetting for 1:N copy

What causes this issue?

You want to copy plan data from one object to another object or to
several objects (1:N copies) and have chosen the "Reset and overwrite"
option.

System Response

Plan data of the target objects that already exists is overwritten,
provided that it has been planned in the reference object. Records only
planned in the target objects are not reset during the 1:N copy.
The result of this is that there may be more plan records in the target
objects than in the reference object after a 1:N copy.

How to fix this error?

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.