EKF2 failsafe after several successful flight

On a flight day we had some working test without any issues, but around the fifth takeoff we had some casualities. In loiter mode, the FC initiated the EKF failsafe. The failsafe option was land.
The critical message were the following:
-EKF variance
-GPS glitch

Based on the log file (811.9 KB), the NKF4.SP, NKF4.SM and the NKF4.SV (so the position, the compass and the velocity measurement), all of them were above 1.

Only the landing sole was broken because the drone technically landed but also drifted horizontally so it has landed in an unfavorable angle.
After the incident, we replaced the broken physical parts, we tried to fly the drone carefully. The drones was hovering for like 2-3 seconds, then started to drift sideways without input. we quickly switched to Alt Hold so there wasnt any incident this time. The log said the same about NKF4 parameters.

We haven’t found the issue, so we could use some help from you guys.