Well, in my stats file I see pkt/stream on wrong thread counter. How does this affect ips results? What problems it creates?
This means that some network packets have been seen on a different thread as the rest of the flow. So the impact might be missing detection or even dropped packets at one point.
A longer discussion can be seen here Optimization #2725: stream/packet on wrong thread - Suricata - Open Information Security Foundation
Otherwise feel free to tell use what version of Suricata you are running, how you run it, how the suricata.yaml looks like and share the stats.log