V0.29 Performance Issue with Decidim: "Retry Later" errors with more than 10 concurrent users on a high-spec server

We are experiencing a performance bottleneck with our Decidim v0.29 installation and would appreciate any guidance you can offer.

The Problem: Our platform works perfectly with a few users in a production configuration, but as soon as we exceed approximately 10 concurrent users, all clients start receiving intermittent "Retry Later" error pages. We have confirmed this behavior using Locust for load testing, and we can provide the test results.