Try turning off the VPS. It could be an issue with that. If you can upload your latest flight log that exhibits the issue, we might be able to tell you if it is an issue with the VPS. Upload to the link below ( Instructions are on the link) and place a link back here to that.
Not sure if you can individually turn off OA and VPS. The VPS is still on in this data. It does look a bit odd, but not overly so. Turn the VPS ( Vision Positioning ) Off. Obstacal avoidance is not a factor. And try another flight. If that appears to be off as far as altitude goes ( Greater than 20 ft) which can occur with the barometer, then we will need the aircraft .dat file as mentioned above to look farther.
Also, flying basically straight up is not going to tell very much regarding the VPS activity. Unless it is really off or intermittently working. Terrain changes are needed to see that. At lower altitudes. You need to try and duplicate the flight in question with the VPS turned off to note your altitude in comparison.