I used the FileImporter to import 300 000 documents. After 200 000 documents imported, I have the following error :

2019-02-03T22:43:42,630 ERROR [ImporterExecutorMainThread] [org.nuxeo.ecm.platform.importer.executor.jaxrs.HttpFileImporterExecutor] Task exec failed
java.lang.IllegalStateException: unknown connection org.nuxeo.ecm.core.storage.sql.ra.ConnectionImpl@4ef63d7b in org.nuxeo.ecm.core.storage.sql.ra.ManagedConnectionImpl@212dcae6
    at org.nuxeo.ecm.core.storage.sql.ra.ManagedConnectionImpl.removeConnection(ManagedConnectionImpl.java:254) ~[nuxeo-core-storage-sql-10.3.jar:?]
    at org.nuxeo.ecm.core.storage.sql.ra.ManagedConnectionImpl.close(ManagedConnectionImpl.java:264) ~[nuxeo-core-storage-sql-10.3.jar:?]
    at org.nuxeo.ecm.core.storage.sql.ra.ConnectionImpl.close(ConnectionImpl.java:114) ~[nuxeo-core-storage-sql-10.3.jar:?]
    at org.nuxeo.ecm.core.storage.sql.coremodel.SQLSession.close(SQLSession.java:132) ~[nuxeo-core-storage-sql-10.3.jar:?]
    at org.nuxeo.ecm.core.api.local.LocalSession.closeInThisThread(LocalSession.java:180) ~[nuxeo-core-10.3.jar:?]
    at org.nuxeo.ecm.core.api.local.LocalSession.destroy(LocalSession.java:193) ~[nuxeo-core-10.3.jar:?]
    at org.nuxeo.ecm.core.api.CoreSessionServiceImpl.releaseCoreSession(CoreSessionServiceImpl.java:86) ~[nuxeo-core-10.3.jar:?]
    at org.nuxeo.ecm.core.api.CoreInstance.closeCoreSession(CoreInstance.java:133) ~[nuxeo-core-api-10.3.jar:?]
    at org.nuxeo.ecm.core.api.local.LocalSession.close(LocalSession.java:154) ~[nuxeo-core-10.3.jar:?]
    at org.nuxeo.ecm.platform.importer.base.GenericMultiThreadedImporter.run(GenericMultiThreadedImporter.java:223) [nuxeo-importer-core-10.10-SNAPSHOT.jar:?]
    at java.lang.Thread.run(Thread.java:748) [?:1.8.0_201]

I'm not sure to understand the error.

Thanks for any help.