If you did not enter the Form 1099-K directly through the Schedule E Rental Income and Expenses section of your return, try entering them there. That will automatically tie them to the rental property.
If you still get flags, delete the Form 1099-K completely and report all of the income from both forms as 'other income' not on a Form 1099-MISC or 1099-K. It is more important that it be reported as income for the property than it is to clear some error flag to enter the actual Form 1099-K. Just keep the forms with your records in the unlikely event you are questioned about it.
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