If your CAS is shutting down frequently, then there are a number of troubleshooting approaches to attempt. There are 2 services: “master” and “admin”. A number of articles are listed here to identify and rectify problems with each service.
The “master” service is responsible for communicating with your Terminals/BATMs. It handles the transactions, and without it - your BATMs will not connect or function.
The “admin” service produces the web page that you’re already familiar with. It enables you to change the settings for CAS, and those changes are then applied to the Terminals (once they connect). Without the admin service, you will be unable to view the CAS web page.