index.yaml not always regenerated when pushing helm charts via API - 404s

K8S: 1.18
Chartmuseum: v0.13.1 (no cache-interval configured)

```env:
- name: DISABLE_METRICS
value: "false"
- name: DISABLE_API
value: "false"
- name: ALLOW_OVERWRITE
value: "true"
- name: CACHE
value: redis
```

```
GET /ccdp/stable/api/charts/ccdp-om-inbound-service/release-1.61.0-dev699051
HTTP/1.1 404 Not Found
Date: Tue, 27 Apr 2021 22:21:32 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 57
Connection: keep-alive
X-Request-Id: dc61e2062300687cbae84e6fc9f744a6
Strict-Transport-Security: max-age=15724800; includeSubDomains
{"error":"improper constraint: release-1.61.0-dev699051"}
```

Though when we checked in the S3 bucket under /ccdp/stable, we do find the helm chart [ccdp-om-inbound-service-release-1.61.0-dev699051]. Upload always seems to work though not always index.yaml gets regenerated. Long story short, if a 404 is returned then we do not deploy (not in automated manner).

We have tried to delete index-cache and restart chartmuseum - problem continues to occur!