After upgrading from 1.3.0 to 1.4.3, lastTaskFailures are no longer reported correctly. This seems to be resolved when the app is restarted (meaning all Mesos tasks are killed and replaced). This might be related to the task -> instance abstraction and related migration/taskId changes.
Since my upgrade to 1.4.3, I've no more feedback on task failures in the Debug tab > Last Task Failures.
Same using the API.
This is very painful since end-users always ask to operators for getting informations about task failures (OOM, exit 1, agent disconnected, etc.).
This is trivial to reproduce: launch an app, kill it on the agent (kill -9), it is rescheduled, but absolutely no message on the UI.