Px4flow wrong zero bias/value when the quad is just sitting

Greetings. I have a problem with my px4flow camera, attached to a quadcopter running an ArduCopter.

Per the setup instruction, log reading of body and flow must coincide, but when I tried putting the quad indoor, outdoor, and about 5 points in between, the indoor values don’t coincide

I think it’s supposed to be zero, though maybe a bit noisy. The zero bias varied between those points (negative X and positive Y with varying maximum, the worst at 2 on the graph), with exact coincidence achieved outside, under the sunlight.

I looked for similar problems everywhere, but no-one mentioned about wrong zero bias. I don’t have any idea either about what might have caused it. I have turned off all lights that might have any flicker, but the problem persists.

Attached is a photo of the log (pardon me, it’s kind of a field situation). The erratic values are when I’m moving the quad between points, so it’s not about that. The rightmost is outside, leftmost inside.

Any help would be appreciated.

For help with ArduPilot, best to ask at discuss.ardupilot.org