Well that's what the error seems to indicate. But no document has FName as a value anywhere in my data. I've done many tests with deleting the index and reingesting my CSVs and looking at each in detail. What really seems to be the problem is that some of the CSV files have empty cells in some of the columns, so you get something that looks like this:
Timestamp,Map,Untagged,ProgramSize,GenericPlatformMallocCrash,FName,Stats,EnginePreInit,FileSystem,ThreadStack,UObject,CsvProfiler,Localization,ConfigSystem,InitUObject,OOMBackupPool,RHIMisc,Meshes,RenderTargets,Textures,Shaders,RenderingThread,UI,AssetRegistry,AsyncLoading,StaticMesh,PhysX,Materials,Audio,Animation,EngineInit,AudioMixer,AudioPrecache,EngineMisc,LoadMapMisc,TaskGraphMiscTasks,GC,Particles,AudioDecompress,AudioFullDecompress,AudioRealtimePrecache,PSO,FMallocUnused,TrackedTotal,Total,Untracked,WorkingSetSize,PagefileUsed,StreamingManager,Networking,
2020-01-29T15:01:22.121Z,Outpost_P,8.07,0.00,3.82,8.88,3.67,17.19,13.32,6.44,126.63,0.00,4.17,1.73,1186.43,32.00,4.18,69.26,225.37,236.06,28.25,0.92,1.92,21.28,11.09,0.83,2.30,0.73,31.10,31.98,0.12,12.73,0.05,0.03,2.18,0.58,0.00,0.02,0.00,159.73,7.03,0.00,97.23,2357.34,6882.60,4658.29,2068.58,2565.27,
2020-01-29T15:01:52.129Z,Outpost_P,9.48,0.00,3.82,8.88,4.92,16.95,14.38,6.45,135.14,0.00,4.17,1.73,1186.43,32.00,4.19,84.03,367.23,305.11,27.47,4.03,19.73,21.28,7.01,0.83,2.30,0.74,31.97,31.97,0.12,13.05,0.05,8.56,2.01,6.93,0.02,0.02,0.00,159.73,7.03,0.05,43.10,2573.00,7019.62,4490.92,2129.38,2879.29,0.07,
2020-01-29T15:02:22.132Z,Station_Lobby,10.29,0.00,3.82,9.13,5.03,16.93,12.26,6.45,120.96,0.00,4.17,1.73,1186.43,32.00,4.27,135.80,440.53,591.12,33.19,5.18,10.73,21.28,8.10,15.57,14.51,0.95,35.01,32.07,0.12,16.50,0.05,21.19,7.18,13.16,0.02,0.18,0.00,182.14,8.25,0.14,47.64,3055.59,7408.83,4401.08,2279.37,3448.17,0.49,1.01,
2020-01-29T15:02:52.139Z,Station_Lobby,10.10,0.00,3.82,9.13,5.03,16.93,12.26,6.45,120.83,0.00,4.17,1.73,1186.43,32.00,4.27,132.23,381.67,590.21,33.18,5.40,10.43,21.28,7.98,15.57,14.52,0.95,34.97,32.07,0.09,17.65,0.05,21.15,7.18,13.35,0.03,0.18,0.00,186.42,8.31,0.17,38.67,2988.37,7289.51,4339.95,2253.25,3358.62,0.49,0.99,
As you can see the last few columns don't have values in the first few rows. I believe the error is related to this situation. I've tried many combinations of these parameters and have tried them set to true and false in various combinations. None of this seem to fix this problem. I'm almost thinking the CSV plugin might have a bug.
autogenerate_column_names => false
autodetect_column_names => true
skip_empty_columns => true
skip_empty_rows => true
skip_header => true