Indices in delete phase are actually not being deleted

Actually, a duplicate subject, but this one is no longer an issue related to the kibana bug. I just upgrade my cluster to 7.13 and the issue remains. My indices are not deleted in the "delete" phase of ilm.

The ILM settings seem correct (i.e. include the "delete" subkey in the "action" key) :

{
  "policy": {
    "phases": {
      "hot": {
        "min_age": "0ms",
        "actions": {
          "set_priority": {
            "priority": 100
          }
        }
      },
      "delete": {
        "min_age": "62d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}

The ILM is actually applied to my indices, as I can view indices that should have been deleted when I select "ilm.phase:(delete)" in index management.

What could be wrong ? Which logs to look at to troubleshoot ilm ?

Thanks in advance for any hint.

Can you share the output of the ILM Explain API for such an index?