The Netlify team experienced partial outages in their build network during September, causing degraded service on three separate days. The proximate cause of these incidents varied, but two root causes were shared: a change to the background processing system and an issue with the message queueing system. These issues were exacerbated by traffic from spam users, which caused further degradation. After the last incident, Netlify deployed a permanent fix for the background processing system stalling and has improved the reliability of their message queueing system. They have also implemented safeguards to prevent abuse by spammers and are working on improving their build system and customer communication. The team is prioritizing service stability and customer experience in their future improvements.