How can I prevent Input.GetAxis from sporadically reporting deltas of 0.0?

I'm using the mouse to drag an object around. On every single frame, I use that object's change in position to drive certain effects (like rotation, color, etc.)

Unfortunately, these effects were very jittery, even under smooth, constant mouse movement. So I decided to log Time.frameCount, Input.mousePosition, and Input.GetAxis deltas inside an Update method. Here's what that looks like while making smooth circles with the mouse:

 Frame: 31 Position: (477.3, 230.8, 0.0) Delta: (1.8, -1.3)
 Frame: 32 Position: (477.3, 230.8, 0.0) Delta: (0.8, -0.4)
 Frame: 33 Position: (522.5, 217.5, 0.0) Delta: (3.5, -0.6)
 Frame: 34 Position: (522.5, 217.5, 0.0) Delta: (0.0, 0.0) <--
 Frame: 35 Position: (565.5, 220.4, 0.0) Delta: (3.7, 0.9)
 Frame: 36 Position: (565.5, 220.4, 0.0) Delta: (0.0, 0.0) <--
 Frame: 37 Position: (586.3, 239.0, 0.0) Delta: (1.3, 2.2)
 Frame: 38 Position: (589.3, 260.5, 0.0) Delta: (0.2, 1.4)
 Frame: 39 Position: (589.3, 272.4, 0.0) Delta: (-0.2, 2.4)

For some reason Input regularly fails to update the mouse on some frames, as seen on frames 34 and 36 above.

Things I've tried:

• Swapping out my mouse and using the MacBook trackpad to rule out hardware polling issues. (same results)

• Caching deltas and reusing the previous when 0.0 is detected, correcting for missed frames after. (feels kinda "swimmy")

• Calculating my own deltas using mousePosition (same results, naturally)

• Lerping the mouse-driven object's position. (degrades response time)

It's been suggested that Input is only updated 20 times per second (or less) under constant mouse movement. I'm testing at 60 fps, so that would explain the behavior I'm seeing.

But I'm at wit's end as to how to fix or compensate for this. For example, how could you possibly create a smooth first person shooter when view angle is directly driven by mouse movement but the mouse is considered momentarily stationary at least 1 out of every 20 rendered frames?

Thanks for any insights!