With ECW v3 Writer I get the following error message:
ECW writer: An invalid parameter was used : date and projection setting are invalid.
The coordinate system used is EPSG:2056/EPSG:21780.
With the coordinate systems UTM / LL-WGS84 the ECW v3 Writer works correctly!
Tested with FME 2019.2.1.0 (Build 19813) WIN64 and FME 2020 Beta (Build 20153) WIN64.