Grails null identifier error appearing sometimes without explanation - postgresql

Question

I have a production app on grails 2.5.6 using postgres and deployed on tomcat 8. I sometimes have a null identifier exception when trying to save in any entity.
When i restart tomcat everything is fine.
My problem is the frequency is not know sometimes it's happens sometimes not,
if someone have any idea of this error is it possible to help.
{
2020-03-15 11:24:52,456 [http-nio-8080-exec-10] ERROR errors.GrailsExceptionResolver -
TransientObjectException occurred when processing request: [POST] /secur/pays/save
The given object has a null identifier: com.referentiel.Pays. Stacktrace follows:
org.hibernate.TransientObjectException: The given object has a null identifier: com.referentiel.Pays
at com.referentiel.PaysController.$tt__save(PaysController.groovy:138)
at grails.plugin.cache.web.filter.PageFragmentCachingFilter.doFilter(PageFragmentCachingFilter.java:198)
at grails.plugin.cache.web.filter.AbstractFilter.doFilter(AbstractFilter.java:63)
at grails.plugin.multitenant.core.servlet.CurrentTenantServletFilter.doFilter(CurrentTenantServletFilter.java:53)
at grails.plugin.springsecurity.web.filter.GrailsAnonymousAuthenticationFilter.doFilter(GrailsAnonymousAuthenticationFilter.java:53)
at grails.plugin.springsecurity.web.authentication.logout.MutableLogoutFilter.doFilter(MutableLogoutFilter.java:62)
at grails.plugin.springsecurity.web.SecurityRequestHolderFilter.doFilter(SecurityRequestHolderFilter.java:59)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
}