Sorry I am so taken aback with your comment, shaming your team members for breaking build is a big no no in my opinion. Code is meant to be broken because that's when the maximum learnings and opportunities for improvement happen. I don't want "stable" build and "broken" team. I heard numerous stories of sr. software engg breakings stuff and have interesting insights to share afterwards. In fact I'd encourage to experiment more with the code base, go where they feel uncomfortable. If something goes wrong I am behind them. If a build is broken it's on me not the team member I am supporting.
PS: In similar situation as OP, leading team of 4 jr software engg.
PS: In similar situation as OP, leading team of 4 jr software engg.