Investigate task failure root cause analysis

What exactly is off in this task? It is a regular epic and was doing what it was supposed to? What is the root cause? 

Root cause: prod epic 10252 was correct; its Plan stage dead-ended because the Epic pipeline had no document-only exit (Plan's only terminal `coders` needs ≥1 coder, operator decided "no coder tasks"). Fixed (ADR-0172): Plan may settle `analysis` = nothing to build, CP stamps `no_build`, epic completes on its analysis children with the plan's report as final report; late appends refused. PR #7043 queued on the merge lane after a green quick gate, 877+585 API and 141 web tests, and a blind review lane whose HIGH/MEDIUM findings were fixed. Visual check done: Outcome panel shows the Report link. Jaah Deploy runs only after the lane merges to develop, so it could not be watched from this session. Recover 10252 by Reset + Start of its Plan child. Memory: used mem-25288, mem-18424; proposed 1 gotcha.