ILM doesn't work after upgrade from 6.7 to 7.2

Hello!

Recently I upgraded from 6.7 to 7.2 (non-OSS free edition, upgraded with entire cluster restart). Previously I've been using ILM policies and they were working like a charm since release. But after I upgraded, they partly stopped. Indices with short lifetime (I mean, created already on 7.2) are rotating, while old indices, created under 6.7 or older are ignoring policies. If I search indices with Kibana, all of them are covered by ILM, while not rotating.

For example, this is ILM explain output of the index that should've been rotated (policy - delete after 90 days):

{
  "indices" : {
    "shrink-openapi-2019.04.28" : {
      "index" : "shrink-openapi-2019.04.28",
      "managed" : true,
      "policy" : "openapi",
      "lifecycle_date_millis" : 1556409515689,
      "phase" : "cold",
      "phase_time_millis" : 1561593545477,
      "action" : "complete",
      "action_time_millis" : 1561593572636,
      "step" : "complete",
      "step_time_millis" : 1561593572636,
      "phase_execution" : {
        "policy" : "openapi",
        "phase_definition" : {
          "min_age" : "60d",
          "actions" : {
            "freeze" : { },
            "set_priority" : {
              "priority" : 30
            }
          }
        },
        "version" : 6,
        "modified_date_in_millis" : 1558542408695
      }
    }
  }
}

And here is policy:

{
  "openapi" : {
    "version" : 1,
    "modified_date" : "2019-07-17T12:08:26.644Z",
    "policy" : {
      "phases" : {
        "warm" : {
          "min_age" : "30d",
          "actions" : {
            "forcemerge" : {
              "max_num_segments" : 25
            },
            "set_priority" : {
              "priority" : 50
            },
            "shrink" : {
              "number_of_shards" : 1
            }
          }
        },
        "cold" : {
          "min_age" : "60d",
          "actions" : {
            "freeze" : { },
            "set_priority" : {
              "priority" : 0
            }
          }
        },
        "hot" : {
          "min_age" : "0ms",
          "actions" : {
            "set_priority" : {
              "priority" : 100
            }
          }
        },
        "delete" : {
          "min_age" : "90d",
          "actions" : {
            "delete" : { }
          }
        }
      }
    }
  }
}

Is there any way to diagnose my problem and fix it? Sure, there is curator available, but I think it's not the right solution...

Solved. The reason was that I had one index linked to non-existing policy. After I removed policy from that index, everything works fine.