To handle unexpected errors gracefully in a custom subscription center, wrapping the code in a Server-Side JavaScript (SSJS) Try/Catch block is recommended.

Try/Catch Block: Using a Try/Catch block in SSJS allows the developer to catch and handle exceptions, providing a mechanism to manage errors without disrupting the user experience.

SSJS Example:

<script runat="server"> Platform.Load("Core", "1"); try { // Code that may throw an error } catch (e) { // Handle the error Write(Stringify(e)); } </script>

Salesforce Server-Side JavaScript (SSJS) Guide