This is because probably caused by the following bugs:
15940804 - The LDom Control Domain OS asset is missing for the t5120 therefore it's unable to successfully provision Solaris 11.1.1 CDOM on a t5120 asset - see workaround above
15818412 - delete asset is not properly cleaning the __local mbeans in the domain model - Fixed in DU3
To reapply the deployment plan, delete the access point and rediscover. Still the plan fails upgrade to the latest version of Ops Center.