When retrieving a transition instance, its ID may change although in fact the very same transition instance still exists. This may lead to confusing behavior when working with the activity/transition instance tree.

Example:

ActivityInstance activityInstance = runtimeService.getActivityInstance(processInstance.getId());
TransitionInstance transitionInstance = findTransitionInstanceIn(activityInstance);

runtimeService.cancelTransitionInstance(transitionInstance.getId());

The last instruction may fail although the transition instance (aka async job) still exists.

Impact on Cockpit:
When multiple users inspect a process instance at the same time and both try to modify the instance (not necessarily in parallel), modification may fail due to this bug.

The reason is execution tree expansion/compaction and the implementation that uses the IDs of the executions performing the async job as the transition instance ID. After expansion/compaction, the execution may be a different one and in effect, the transition instance ID has changed.