[Bug] Inconsistent world coordinates returned by pickObject method

Description

When using the pickObject method to transform screen coordinates to world coordinates, the resulting coordinates (x, y, z) vary slightly and seem to be influenced by the position of the camera. This inconsistency makes it difficult to accurately interact with 3D objects on the map.

I have a 3D object with a fixed height of 15. However, the unproject method returns slightly different z values for the same point, even though the height should consistently be 15.

Here are some example coordinates that were obtained when hovering over a 3D object on the map. The object has a fixed height of 15, but the z values returned are slightly different each time:

Expected height: 15

Unprojected coordinates:

(3) [14.967373591089833, 55.215464098258174, 15.006034213629]
(3) [14.967371362548931, 55.21546726508324, 15.00713966500024]
(3) [14.96737136262501, 55.215467265098205, 15.00713966500024]
(3) [14.967368298183448, 55.21547185649847, 15.008745031010902]
(3) [14.967368298269019, 55.215471856518064, 15.008745031010902]
(3) [14.967366348143466, 55.2154759730605, 15.009797201422398]
(3) [14.967366348237713, 55.21547597308487, 15.009797201422398]

Flavors

• Script tag
• React
• Python/Jupyter notebook
• MapboxOverlay
• GoogleMapsOverlay
• CartoLayer
• ArcGIS

Expected Behavior

The (x, y, z) coordinates should be consistent for the same point on the object, and the z value should be exactly 15 regardless of the camera's position.

Steps to Reproduce

Move the camera to different positions.
Use the unproject method to convert screen coordinates back to world coordinates.
Observe the variation in the (x, y, z) coordinates for the same point on the object.

Environment

• Framework version: deck.gl@8.9.34

Logs

No response

Start by reproducing the issue with the React flavor on deck.gl@8.9.34, focusing on the pickObject and unproject methods while moving the camera. Trace the coordinate conversion entry points and compare repeated results for a fixed-height object; done means the same point returns consistent coordinates and a z value of 15.