When executing the API "/controller/management/servers/{serverTemplateId}/containers/{containerId}" in the headless controller, we got 500 internal server error and the following message is logged in the server.log file: 

*******************************************

2022-09-16 14:19:08,649 DEBUG [org.kie.server.controller.rest.RestSpecManagementServiceImpl] (default task-4) Received update container spec request for server template with id kieserver-01
2022-09-16 14:19:08,670 DEBUG [org.kie.server.controller.rest.RestSpecManagementServiceImpl] (default task-4) Container spec is ContainerSpec{releasedId=evaluation:evaluation:1.0.0-SNAPSHOT, configs=

, status=STARTED} ContainerSpecKey{id='evaluation_1.0.0-SNAPSHOT', containerName='evaluation', serverTemplateKey=null}
2022-09-16 14:19:08,671 ERROR [org.kie.server.controller.rest.RestSpecManagementServiceImpl] (default task-4) Save container spec request for server template id kieserver-01 failed due to null: java.lang.NullPointerException
    at org.kie.server.controller.api.model.spec.ServerTemplate.hasMatchingId(ServerTemplate.java:264)
    at org.kie.server.controller.impl.service.SpecManagementServiceImpl.updateContainerSpec(SpecManagementServiceImpl.java:114)
    at org.kie.server.controller.rest.RestSpecManagementServiceImpl.updateContainerSpec(RestSpecManagementServiceImpl.java:112)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)

...

*******************************************

However, the same API for GET and PUT works fine. 

If we use Business Central or Decision Central, this POST REST API works fine as well.