FM2019 DITA OT output generation fails

When trying to generate xhtml or htmlhelp output, the log gives this error:

BUILD FAILED
C:\Adobe FrameMaker 2019\fminit\ditafm\DITA-OT\build.xml:41: The following error occurred while executing this line:
C:\Adobe FrameMaker 2019\fminit\ditafm\DITA-OT\plugins\org.dita.base\build_preprocess.xml:42: Failed to run pipeline: Illegal character in path at index 8: Creating a new data test.xml#id168ADB010C9/id17C3F0820AD

How can I correct this and generate the output successfully? Thanks!