Vulkan Depth Buffer Readback Problem

Our application does read back of the depth buffer after rendering. We are getting what looks like corruption in the depth buffer… or we suspect that we may be reading back the buffer before rendering is done - although we have tried different approaches of barriers and synchronization. The depth buffer is in format VK_FORMAT_D32_SFLOAT.

On one system, an older Linux workstation with GPU GTX 760, running driver 440.82, the results are as expected (see attached image with smooth gray scale). But in all other system, including Xavier AGX we get gray scale with “spots” (See attached image with spots)

I would appreciate anyone’s insight on how to solve this problem.