RunThese24H finished but failed during clean up with "Too many open files" FileNotFoundException or FileSystemException

The tail of stress stdout is:
Channel.ReadTests.read02_07(ReadTests.java:977)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:565)
at javasoft.sqe.javatest.lib.MultiTest.invokeTestCase(MultiTest.java:406)
at javasoft.sqe.javatest.lib.MultiTest.run(MultiTest.java:195)
at javasoft.sqe.javatest.lib.MultiTest.run(MultiTest.java:127)
at javasoft.sqe.tests.api.java.nio.channels.AsynchronousFileChannel.ReadTests.main(ReadTests.java:52)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:565)
at applications.kitchensink.process.stress.modules.JckStressModule$TestRunner.lambda$runTest$1(JckStressModule.java:307)
at java.base/java.lang.Thread.run(Thread.java:1474)
Caused by: java.lang.ClassNotFoundException: javasoft.sqe.tests.api.java.nio.CleanupUtils
... 13 more
==== read01_08 ====
TEST SETUP FAILED: Unexpected javasoft.sqe.tests.api.java.nio.FileUtils$Exception: Unexpected failure
    Caused by java.nio.file.FileSystemException: /opt/mach5/mesos/work_dir/slaves/d2398cde-9325-49c3-b030-8961a4f0a253-S121080/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/e84459db-5e94-4ceb-8bb6-33c06ab9c5e2/runs/12098072-1c64-4113-954e-bf8482170597/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_runthese_RunThese24H_java/scratch/0/jckWorkDir/rd15: Too many open files
javasoft.sqe.tests.api.java.nio.FileUtils$Exception: Unexpected failure
at javasoft.sqe.tests.api.java.nio.FileUtils$RealFile.create(FileUtils.java:342)
at javasoft.sqe.tests.api.java.nio.channels.AsynchronousFileChannel.AFCTestCase.setup(AFCTestCase.java:62)
at javasoft.sqe.tests.api.java.nio.channels.AsynchronousFileChannel.AFCOpenedTestCase.setup(AFCTestCase.java:163)
at javasoft.sqe.tests.api.java.nio.Nio2TestCase$Single.run(Nio2TestCase.java:252)
at javasoft.sqe.tests.api.java.nio.channels.AsynchronousFileChannel.ReadTests.read01_08(ReadTests.java:1009)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:565)
at javasoft.sqe.javatest.lib.MultiTest.invokeTestCase(MultiTest.java:406)
at javasoft.sqe.javatest.lib.MultiTest.run(MultiTest.java:195)
at javasoft.sqe.javatest.lib.MultiTest.run(MultiTest.java:127)
at javasoft.sqe.tests.api.java.nio.channels.AsynchronousFileChannel.ReadTests.main(ReadTests.java:52)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:565)
at applications.kitchensink.process.stress.modules.JckStressModule$TestRunner.lambda$runTest$1(JckStressModule.java:307)
at java.base/java.lang.Thread.run(Thread.java:1474)
Caused by: java.nio.file.FileSystemException: /opt/mach5/mesos/work_dir/slaves/d2398cde-9325-49c3-b030-8961a4f0a253-S121080/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/e84459db-5e94-4ceb-8bb6-33c06ab9c5e2/runs/12098072-1c64-4113-954e-bf8482170597/testoutput/test-support/jtreg_closed_test_hotspot_jtreg_applications_runthese_RunThese24H_java/scratch/0/jckWorkDir/rd15: Too many open files
at java.base/sun.nio.fs.UnixException.translateToIOException(UnixException.java:100)
at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:106)
at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:111)
at java.base/sun.nio.fs.UnixFileSystemProvider.newFileChannel(UnixFileSystemProvider.java:213)
at java.base/java.nio.channels.FileChannel.open(FileChannel.java:301)
at java.base/java.nio.channels.FileChannel.open(FileChannel.java:353)
at javasoft.sqe.tests.api.java.nio.FileUtils$RealFile.create(FileUtils.java:334)
... 14 more