Grails 4 - Google Cloud Platform deployment keeps restarting - spring

Question

My Grails 4 application, deployed to GCP appears to be trying to start up after being deployed but never comes up properly. Application requests return a 500 response. There are no errors or clues with DEBUG log level output at the root level.
The same application runs fine locally in development mode.
The production configuration is as per the Grails 3 deployment (to GCP) guide except for the adjustments that were necessary to make it work for Grails 4/Java 11.
Most of the bootstrapping appears to carry out as expected;
Spring Security configures successfully
Spring Security REST configures successfully
Spring beans are registered
Connects to Cloud SQL instance
Database schema is created (by Liquibase)
Plugins are loaded successfully
Then it gets to the following familiar lines of output logging;
INFO --- [main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
INFO --- [main] o.a.coyote.http11.Http11NioProtocol : Initializing ProtocolHandler ["http-nio-8080"]
INFO --- [main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
INFO --- [main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.17]
and restarts..
while normally, the next phase of bootstrapping (happens locally) would be;
[restartedMain] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
[restartedMain] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 42018 ms
Probably a long shot question but any level of clues or suggestions would be much appreciated.
I've run out of doors to open. :-(

Answer 1

You could try to update Tomcat version just in case.
But looking at Grails documentation:
https://docs.grails.org/latest/guide/upgrading.html
There's some configuration made when you upgrade to Grails 4 from
Grails 3.3.x to prevents the server from restarting when views or
message bundles are changed.
Either modifying a gsp in Grails 4 M2 cause the application to restart.
https://github.com/grails/grails-core/issues/11284