Duplication error in Gradle build process

During the build process using
./gradlew clean xnatPluginjar
I get this error:

Task :sourcesJar FAILED

FAILURE: Build failed with an exception.

What went wrong: Execution failed for task ':sourcesJar'. Entry schemas/biosignals/biosignals.xsd is a duplicate but no duplicate handling strategy has been set. Please refer to https://docs.gradle.org/7.3.3/dsl/org.gradle.api.tasks.Copy.html#org.gradle.api.tasks.Copy:duplicatesStrategy for details.

I fixed it temporary with
duplicatesStrategy = DuplicatesStrategy.EXCLUDE
in task sourcesJar of the gradle settings. I used gradle 7.3.3