EPiServer Find (13.0.1) Sort by Date. The returned Hits is not properly sorted by the sort value

{
"_index": "index15455-en",
"_type": "SeriesNode",
"_id": "CatalogContent_70d204e7-487d-4a41-91d0-52affe791681_en",
"_score": null,
"fields": {},
"sort": [
1549027800000
]
},
{
"_index": "index15455-en",
"_type": "SeriesNode",
"_id": "CatalogContent_24073783-ba86-4c6e-8ac6-5153860f5f5b_en",
"_score": null,
"fields": {},
"sort": [
1548871200000
]
}

If you check the Hits from find. the sort value is not properly ordered by teh value. 1548871200000 < 1549027800000 for above case, then the document having sort value of 1549027800000 should be behind the document having sort value of 1548871200000