How do you make your CTO better?

We are a lean Fintech SAAS team (25 ppl) and have scaled quite well. Funded by marquee names ($1M) and on track to profitability. But the early scale we had was made by the blue chip clients me and my co-founder (CTO) personally sold to. In this process, my co-founder transferred into client tech relations and led every integration himself, and post go live, gave product support as well.

Today, this is problem as clients call him directly and avoid a escalation matrix. He will then position the product/tech team to the issue made by the loudest client, thereby breaking sprints and delaying new deliveries. Please suggest how to approach this situation.

Appreciate the help