Strange I-485 update

I have got a strange I-485 update today.
In this January, the my I-485 updated and informed me that USCIS sent me something and it was returned to USCIS.
In May, it updated again saying that the documents they mailed me in January is not important.
Today, the I-485 updated with the exact message sent to me in January.
This is strange. I guess the guys who are in charge of sending online messages made a mistake today. My priority date has not reached yet.
Anybody else has similar experience or has a good explanation?