The poetry lock command generated a lock file containing 2 different versions of the same package.

[[package]]
name = "grpcio"
version = "1.49.1
...
[[package]]
name = "grpcio"
version = "1.51.3"
...

This is due to the following dependency constraint in one of the package:

grpcio = [
    {version = ">=1.42.0", markers = "python_version >= \"3.10\" and sys_platform != \"darwin\""},
    {version = ">=1.42.0,<=1.49.1", markers = "python_version >= \"3.10\" and sys_platform == \"darwin\""},
]

The export command fails with Dependency walk failed at grpcio (>=1.42.0,<=1.49.1)

This happens because the first analyzed dependency choose the 1.51.3 version first. When the grpcio (>=1.42.0,<=1.49.1) dependency is analyzed (afterwards), the 1.49.1 version is being filtered out here.