Sometimes, webhooks aren't running

Hi,

We're using GitLab CE from source. We're running it on CentOS 7. We're using webhooks for commits in several: slack integrations, and custom webhooks (integrated with own made scripts). We're on latest 8.5 version, but I can upgrade it to 8.6, if it needs. I don't know the exact version, where it started, but somewhere in early 8.5.

So, the problem: sometimes, after the commits, the webhooks aren't executed. I can't see our webhook scripts (they're logs every event), and I can't see any message on Slack channel either. If I press the "Test webhook" button manually, they're running as excepted. It's important, that sometimes, the webhooks are working fine... It's not reproducible in every cases.

I've no idea, how can I start creating more detailed logs. Only thing, that I've found that sidekiq.log contains less ProjectWebHookWorker start/done rows...

This issue drives us crazy.

Regards, Peter