Dissonant planet in a non-dissonant system

As the title says. I went to a system that wasn't labeled as dissonant and ot had a dissonant planet. I found a crashed ship but couldn't probe the brain. Like it wouldn't try to find the monolith at all. Turns out it started the mission in a neighboring system. Went there and found another crashed ship. Long story short, I had to get a brain from that system and turn it harmonic to take back to the first system to get that crashed ship. Anybody ever run into this situation? First time for me.