VPN App Connection Troubleshooting

We currently have an Android VPN application, and recently, we've added new servers to our infrastructure. However, we've encountered an issue where, after connecting to one of the new servers, if the app transitions to the background and then returns to the foreground after 20 seconds, the connection is actively terminated. This problem does not occur with the old servers. The issue is quite perplexing, and we require your extensive experience with Android VPNs to help diagnose and resolve this anomaly.