Multiple incident issues created for alerts via Generic Alert Endpoint

Summary

While testing #220065 (closed) I've noticed that multiple incident issues are created for a single incoming Generic Alert.

Moreover, the alerts are not linked to the created issue.

Steps to reproduce

Trigger an alert via the Generic Alert Endpoint:

curl --request POST --data '{"title": "Just testing"}'   --header "Authorization: Bearer <token>"   --header "Content-Type: application/json" https://gitlab.com/gitlab-org/monitor/tanuki-inc/alerts/notify.json

The first issue is (almost) instantly. The duplicates are created later due to Sidekiq retrying a failed job.

Example Project

https://gitlab.com/gitlab-org/monitor/tanuki-inc/

What is the current bug behavior?

I see multiple (4) issues created instead of just one and do not see the alert being linked to the issue.

What is the expected correct behavior?

Create just one issue.

Relevant logs and/or screenshots

Issues	Alerts details
	note Create issue button and the empty Issue Iid

Possible fixes

!33647 (merged)