See this Comm Center thread by Stephen Avery. This is unreal. He had a Plan that was broken:



2022-02-16 21:20:44.6: **[efficiency entry] Plan NGC 2403-Red 300s (13-18) has no observations! Returning eff=0




With Rising Plan Delay set. that caused the FinalPlist to be off from the nUsablePlans (Engine.cs @ 3163), and this caused an ancient "assert" check to force a run time error. This should instead log an "unusual condition" at brief level so it's always logged. It should "never happen" anyway. he apparently hand constructed or edited the Plan.