Adjustment of Status - I-485

Hi Guys, I had my interview on the 7th of January and our interview was great, IO just asked a few questions and look into our album and told us we have enough, strong evidence and she got all she needs. But because of my minor arrest 4 years ago, she said it would take 2-3 weeks for me to get the approval. (additional background checks)

We left the office really happy But since then my online case status never changed as "ready for interview" until today, it changed to "your interview was completed, your case must be reviewed". (both forms I-485, I-130)

It's strange that I got this update 3 months after the interview, most people get these updates same day after the interview or day after. Then 3 months later they get their approval. I was expecting an approval notice..

I just wanted to ask your opinion if you have experienced something similar. Receiving "must be reviewed" update 3 months after the interview and how long should it take for them to conclude with a decision.

Thank you for your time and goodluck all of you!