• I have tested the latest master version from http://builds.jabref.org/master/ and the problem persists

JabRef version JabRef 4.1-dev--snapshot--2017-12-08--master--6f39151a7 on Windows 7x64 with Java jre1.8.0_151

Steps to reproduce:

1. A custom layoutfile (datacite.layout) was created and placed in the JabRef folder (according to http://help.jabref.org/en/CustomExports)
2. A new custom export filter (DCX) was declared referencing the layoutfile above.
3. An export war created calling java.exe -jar JabRef--master--latest.jar -n -o D:\test.xml,DCX D:\Test.bib
4. Up to this point everthing works as expected
5. The custom layoutfile was modified now using a custom name formatter called DCA (according to http://help.jabref.org/en/CustomExports)
6. The custom name formatter was defined via Preferences->Name Formatter
7. Now the execution of the same export ends with the error
   [AWT-EventQueue-0] WARN org.jabref.logic.exporter.ExportFormat - the following formatters could not be found: DCA
   The created output file shows before every author [Formatter not found: DCA]
   The same result is received using the GUI via File -> Export
   With JabRef Verion 2.9 this was never a problem.

Details
layoutfile datacite.layout contains only the following line causing the error
\format[DCA]{\author}

The name formater too is absolutely simple
Formater Name = DCA
Format string = {ll}, {f.}