Describe the bug
I have a workflow that gets stuck on a regular basis waiting for macOS VMs. See for instance https://github.com/pombredanne/scancode-toolkit/actions/runs/2877397119 where the workflow has been stuck for over 2 hours waiting for macOS runners.
This has been happening to me a couple times over the last week.

To Reproduce
See https://github.com/pombredanne/scancode-toolkit/actions/runs/2877397119
I cannot find any pattern

Expected behavior
The macOS VMs should become available without waiting hours.

Runner Version and Platform

That's the MSFT/GitHub hosted runner

OS of the machine running the runner? OSX/Windows/Linux/...
macOS

What's not working?

The log of each stuck job has something like this:

Test POSIX PyPI wheels (macos-12, 3.9)
Started 2h 22m 15s ago
The agent pool assigned to this job has hit their MacOs concurrency limits
Requested labels: macos-12
Job defined at: pombredanne/scancode-toolkit/.github/workflows/scancode-release.yml@refs/tags/v31.0.0rc51
Waiting for a runner to pick up this job...

Job Log Output

There is no log yet.