Fingerprint fee received but they returned 485 photos & supporting documents?

Resubmitted 485 & 765 in March (original submission in Nov 2020 was rejected - additional alien info required reason).
Last week, $1225 was cashed, email said "fingerprint fee received" with receipt number. Am waiting for receipt in mail.
Surprisingly, today I received 485 supporting documents/photos (not the form) and 765 rejection notice (incorrect fee).
For 765 rejection, it may be a mistake by USCIS as there is no fee if filed concurrently, so I will have to file again.
BUT why did they return 485 documents/photos, while keeping the 485 form and cashing $1225 ? Is it a mistake, or do I now expect RFE or 485 denial if they don't have photos etc?
 
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