Here are some files showing an anomaly with yaw running Copter 3.4rc2 last week.
After switching to Stabilize and starting to descend, the Hex did an abrupt uncommanded yaw of about 20 degrees. It went from ~4 to ~341deg. I momentarily reacted then just landed it. The log of the RC inputs show nothing from channel 4 commanding that yaw. Looking further at the log, one can see the Altitude estimate (which was way wrong) is “reset” in the air by nearly 10 meters at that exact moment as well. This issue was on the same vehicle experiencing another issue I posted about here. Not sure if the two are related.
Attached is the relevant log files.