Currently, certain characters in field or table names are not supported for field mapping, specifically "... spaces, hyphens, and other special characters," but sometimes data schemas from IoT devices have spaces in field names, for example:
https://wiki.dragino.com/xwiki/bin/view/Main/User%20Manual%20for%20LoRaWAN%20End%20Nodes/DS03A-NB_NB...
There was enhancement request for GeoEvent: [ENH-000166468: Allow spaces for attribute names from input connectors in Field Mapper for ArcGIS GeoEvent Server], but it was rejected because development team has no plans to support it in GeoEvent Server, as it is now officially a deprecated Esri product, and will not be receiving any future new capabilities (just bug fixes).
However, this enhancement is still needed, but now in ArcGIS Velocity for ArcGIS Enterprise.
