Compacting bucket does not purge tombstoned document

The document has an empty body, is tombstoned and this meta data:

{
  "meta": {
    "id": "PSKh7fwzmdhzy4ROVJIMqClGMJN2::0kz4d65oyb37::shoppingListItem::rn4gntrl4ukv::6226705401c1",
    "rev": "47254-15ad17eed32b00000000000000000000",
    "expiration": 0,
    "flags": 0,
    "type": "json"
  },
  "xattrs": {
    "_sync": {
      "rev": "4-92cb88751d0ed64706f0ab35f2216a56",
      "flags": 1,
      "sequence": 121736929,
      "recent_sequences": [
        121736929
      ],
      "history": {
        "revs": [
          "4-92cb88751d0ed64706f0ab35f2216a56",
          "1-11d846aa02457d6920d1a1f4c86a6324",
          "2-26874d27fbbe44c0f5a970ca57e7004e",
          "3-90eebbfe7956e9c13e378893c96f8bae"
        ],
        "parents": [
          3,
          -1,
          1,
          2
        ],
        "deleted": [
          0
        ],
        "channels": [
          null,
          null,
          null,
          null
        ]
      },
      "cas": "0x00002bd3ee17ad15",
      "value_crc32c": "0x297bd0aa",
      "tombstoned_at": 1561930960,
      "time_saved": "2019-06-30T23:42:40.279627994+02:00"
    }
  }
}

The Tombstone Purge Interval is set to 30 days. The document was tombstoned on 2019-06-30. That is over 30 days ago. I ran compaction twice but the document remains unchanged. Should this document be purged after compaction has completed? What logs can I dig into to find the cause why it wasn’t purged?

Thanks!

Reading some documentation I’ll add that enable_shared_bucket_access is set to true in the SG config.

SG version 2.1.2
CB Server 6.0

I ran this command:

curl -X POST "http://localhost:4985/my_db/_compact" -H  "accept: application/json"

on my dev cluster and it purged many documents. It also seems that it only purged docs which were tombstoned longer than 30 days ago - the set tombstone purge interval.

As far as I can tell this is exactly what I was looking for. I’ll try it in production!

Same problem here!
Couchbase v6.6.2. I have enable_shared_bucket_access: true and Metadata Purge Interval: 1 day.
The sg_tombstones_x1 index counts 18mln items.
If I run this query to get the min tombstoned_at I get a date that is 27 days ago

SELECT RAW millis_to_str(1000*min(META(b).xattrs._sync.tombstoned_at),'1111-11-11')
FROM `my-bucket` AS b USE INDEX (sg_tombstones_x1 USING GSI)  

If I manually run a compaction, nothing happens. Why?

UPDATE:
moving sg_tombstones_x1 to another node via ALTER INDEX caused it to be recalculated and went from 18mln items to 600k items.
Now if I run the query to get the min tombstoned_at I get yesterday