The undeployed completed process instance diagram shows the updated not the original process workflow.

Steps to recreate :
1. Create any sample workflow through business central. For example, you could create a process as simple as: start node+script node+end
2. build and deploy.
3. Menu->Deploy->Execution Servers->Add Deployment Unit.
create a container with name, for example, "container1" and specify the GAV of the project created in step 1. Start the "container1".
4. Manage->Process Definitions, Execute the process and you will get process model of executed flows, Assume process id as 1
5. Stop and delete "container1"
6. Now open the project created in step 1 and make some changes to the process. For example, add one more script node. build and deploy the project.(you could change the version number here but you will see the same result.)
7. Create "container1" with new workflow created in step 6. (they could have the exact same GAV or different GAV, you will see the same result). start the "container1".
8. repeat the step 3 to execute the process.
9. now try to view process id 1 which was execute using old workflow. you will see process model does not have any blocks selected and New modified process flow is displayed. The original process model associated with the process instance id 1 is not displayed.