After I have updated the client ucs_client.sh quits with an error.
Some changes (e.g. when new config lines are being introduced in control/config.conf) require that you run install.sh script again or rebuild the ledger. You may also have a look at the Troubleshooting section if there is some thread that resolves your problem. If your problem still persists afterwards it indicates that there is an error in source code.
You can seek direct support by opening a ticket on discord server or by creating a post in the Troubleshooting section. In addition you can also report the issue on GitHub so that the problem can be fixed.