Ghost webhook-triggered build stuck in Starting Up state

Hello.

I have a small blog which has been working fine for years: https://f70f2d06-bbf5-4bce-bfdb-6b93306c6e7a.netlify.app/

It is a headless Ghost as CMS and then webhooks trigger a build and deploy on Netlify. Recently all deploys triggered via Ghost hook (“Deploy triggered by hook: Ghost update”) show up with “Starting Up” state, but it doesn’t seem like they even initialize/start - there is absolutely nothing in the logs, and they just get stuck in such state until time out and failure.

When I manually trigger the build everything works fine.

This is on free tier, with 1 concurrent build and the issue happens still within free limits.