If a change order has several cost lines linked to the same income requirement, each line shows an info icon warning that it is linked to several costs. This is not an error.
When you approve the change order, the income is set equal to the approved income requirement on each linked line — not distributed between them. This means that if two cost lines are linked to the same income requirement, both get full income, not half each.
If you want the income to be distributed differently, you can break the link on one of the cost lines and instead link it to the correct income requirement manually.