Basic Tests C/C++ MacOS and Basic Tests Node MacOS flakes.
When they fail, I see a bunch of messages saying "file has vanished"

file has vanished: "/tmpfs/src/github/grpc/workspace_c_macos_opt_native/tools/run_tests/sanity/check_qps_scenario_changes.py"
file has vanished: "/tmpfs/src/github/grpc/workspace_c_macos_opt_native/tools/run_tests/sanity/check_shellcheck.sh"
file has vanished: "/tmpfs/src/github/grpc/workspace_c_macos_opt_native/tools/run_tests/sanity/check_submodules.sh"
file has vanished: "/tmpfs/src/github/grpc/workspace_c_macos_opt_native/tools/run_tests/sanity/check_test_filtering.py"
file has vanished: "/tmpfs/src/github/grpc/workspace_c_macos_opt_native/tools/run_tests/sanity/check_tracer_sanity.py"
file has vanished: "/tmpfs/src/github/grpc/workspace_c_macos_opt_native/tools/run_tests/sanity/check_version.py"
file has vanished: "/tmpfs/src/github/grpc/workspace_c_macos_opt_native/tools/run_tests/sanity/core_banned_functions.py"
file has vanished: "/tmpfs/src/github/grpc/workspace_c_macos_opt_native/tools/run_tests/sanity/core_untyped_structs.sh"
file has vanished: "/tmpfs/src/github/grpc/workspace_c_macos_opt_native/tools/run_tests/sanity/sanity_tests.yaml"
rsync warning: some files vanished before they could be transferred (code 24) at main.c(1677) [generator=3.1.3]

https://source.cloud.google.com/results/invocations/9b4b867c-54ba-436a-b188-4e281627fe0d/targets
https://source.cloud.google.com/results/invocations/adb1dbdc-5999-4ad0-a2a0-2a6a2a4fb518/targets