Where the freemarker.template.Configuration is created, the incompatibleImprovements setting shouldn't be left on its default, 2.3.0. It should be set to Configuration.getVersion() (like new Configuration(Configuration.getVersion()), or with config.setIncompatibleImprovements(Configuration.getVersion())).

Why: The plugin doesn't execute the templates, just parses them. As of 2.3.24, all the "incompatible" fixes that affect the parser (not the execution) just makes it stricter by eliminating legacy parser glitches that let through things that are pretty much always just user oversights. Also when 2.3.24 is out, the new ftlh and ftlx file extensions, which affect parsing, will only have effect with incompatibleImprovements 2.3.24.