Hi @Brad Nesom​ , could you provide a bit more information on your workflow? At which stage does this error occur? It would be very helpful if you could share your workspace and a sample dataset with us. Thank you!

this is difficult to do. I think i have only seen this when running with caching turned on. Also I am running a scan of our entire network. the log does show a specific file in the fatal. but if i inspect it with Map3D it is identical to other dwgs that don't get the error in regards to having a CS assigned in map. It is quite mysterious what fme is doing. The log of the file i just ran (without caching) have these lines...

020-09-18 15:36:27|  2.0| 0.0|INFORM|FME Configuration: Using FME Reprojection Engine

2020-09-18 15:36:28|  2.8| 0.8|INFORM|AutoCAD Reader: Using coordinate system named `WY83-EF' as read from file `S:\\SURVEY\\`COGO DATA\\WYOMING\\WYE_NAD83.dwg'

2020-09-18 15:36:28|  2.8| 0.0|INFORM|FME Configuration: Source coordinate system for reader REALDWG_1eREALDWG] set to `WY83-EF' as read from input data

2020-09-18 15:36:28|  2.8| 0.0|INFORM|Coordinate System `WY83-EF' parameters: CS_NAME=`WY83-EF' DESC_NM=`NAD83 Wyoming State Planes, East, US Foot' DT_NAME=`NAD83' EPSG_QD=`1' GROUP=`SPCS83F' MAP_SCL=`1' MAX_LAT=`45.4' MAX_LNG=`-103.76666666666667' MIN_LAT=`40.6' MIN_LNG=`-106.61666666666666' ORG_LAT=`40.5' PARM1=`-105.166666666667' PROJ=`TM' QUAD=`1' SCL_RED=`0.9999375' SOURCE=`Calculated from WY83-E by Mentor Software' UNIT=`FOOT' X_OFF=`656166.6666666666'

2020-09-18 15:36:29|  3.4| 0.6|WARN |Coordinate system named _coordsys does not exist.

2020-09-18 15:36:30|  3.6| 0.2|WARN |Coordinate system named _coordsys does not exist.

as though the CS is there and it's not there.

This is the log of running with caching and the fatal error happens.

2020-09-18 07:41:43| 10.1| 0.6|INFORM|Predefined coordinate system `TX-SC' (NAD27 Texas State Planes, South Central Zone(4204), US Foot) matches dataset coordinate system 

2020-09-18 07:41:43| 10.1| 0.0|INFORM|The OGC definition of the FME coordinate system '_TX-SC_0' is 'PROJCSX"State Plane 27 TX South Central NAD27 US Survey Feet-csref",GEOGCSe"GCS_North_American_1927",DATUM_"D_North_American_1927",SPHEROIDe"Clarke_1866",6378206.4,294.9786982]],PRIMEM2"Greenwich",0],UNITo"Degree",0.0174532925199432955]],PROJECTION2"Lambert_Conformal_Conic"],PARAMETERm"False_Easting",2000000],PARAMETERg"False_Northing",0],PARAMETERo"Central_Meridian",-99],PARAMETERi"Standard_Parallel_1",28.38333333333333],PARAMETER."Standard_Parallel_2",30.28333333333333],PARAMETER."Latitude_Of_Origin",27.83333333333333],UNITt"Foot_US",0.304800609601219241]]'

2020-09-18 07:41:43| 10.1| 0.0|INFORM|AutoCAD Reader: Using coordinate system named `_TX-SC_0' as read from ESRI_PRJ embedded in file `S:\\SURVEY\\`COGO DATA\\TEXAS\\SCOMAD_OC_2D.dwg'

2020-09-18 07:41:43| 10.1| 0.0|INFORM|AutoCAD Reader: Successfully opened the 'Release2004' AutoCAD file 'S:\\SURVEY\\`COGO DATA\\TEXAS\\SCOMAD_OC_2D.dwg'

2020-09-18 07:41:43| 10.1| 0.0|WARN |AutoCAD Reader: Renamed attribute 'C:\\Carlson' to 'C__Carlson' to remove the following invalid characters '<>/\\&$|:!~ ()"@'

2020-09-18 07:41:43| 10.1| 0.0|INFORM|FME Configuration: Source coordinate system for reader R_6cACAD] set to `_TX-SC_0' as read from input data

2020-09-18 07:41:43| 10.1| 0.0|INFORM|Coordinate System `_TX-SC_0' parameters: CS_NAME=`_TX-SC_0' DESC_NM=`NAD27 Texas State Planes, South Central Zone(4204), US Foot' DT_NAME=`NAD27' EPSG_QD=`1' ESRI_WKT=`PROJCS#"State Plane 27 TX South Central NAD27 US Survey Feet-csref",GEOGCSD"GCS_North_American_1927",DATUMt"D_North_American_1927",SPHEROID;"Clarke_1866",6378206.4,294.9786982]],PRIMEM&"Greenwich",0],UNIT,"Degree",0.0174532925199432955]],PROJECTIONt"Lambert_Conformal_Conic"],PARAMETERb"False_Easting",2000000],PARAMETERa"False_Northing",0],PARAMETERu"Central_Meridian",-99],PARAMETERC"Standard_Parallel_1",28.38333333333333],PARAMETER_"Standard_Parallel_2",30.28333333333333],PARAMETER_"Latitude_Of_Origin",27.83333333333333],UNIT_"Foot_US",0.304800609601219241]]' GROUP=`SPCS27' MAP_SCL=`1' MAX_LAT=`30.966666666666665' MAX_LNG=`-91.96666666666667' MIN_LAT=`27.483333333333334' MIN_LNG=`-106.43333333333334' ORG_LAT=`27.83333333333333' ORG_LNG=`-99' PARM1=`30.28333333333333' PARM2=`28.38333333333333' PROJ=`LM' QUAD=`1' SCL_RED=`1' SOURCE=`Snyder, J.P., 1987, Map Projections - A Working Manual' UNIT=`FOOT' X_OFF=`2000000'

2020-09-18 07:41:43| 10.1| 0.0|WARN |AutoCAD Reader: Renamed attribute 'C:\\Carlson' to 'C__Carlson' to remove the following invalid characters '<>/\\&$|:!~ ()"@'

2020-09-18 07:41:44| 10.3| 0.2|WARN |... Last line repeated 289 times ...

2020-09-18 07:41:44| 10.3| 0.0|ERROR |An error occurred while attempting to add a shape to a feature buffer. The error number from ArcObjects is: '-2147220936'. The error message from ArcObjects is: {No spatial reference exists.}

not sure how you want me to send dataset. i could send 1 file but won't be able to send public.