After downloading jbpm-server-7.20.0.Final-dist.zip tried to run bin\standalone.bat.
Imported several demo projects and deployed Dinner_Party.
Then shutdown the server: bin\jboss-cli.bat --connect --command=:shutdown
Than started server again and when tried to open Dinner_Party project got the "Indexing has not finished" and locking exception on console:
19:03:58,514 ERROR [org.uberfire.ext.metadata.io.IndexerDispatcher] (Thread-228) Indexing error for indexer [id=org.drools.workbench.screens.guided.rule.backend.server.indexing.GuidedRuleDslrFileIndexer]: java.lang.RuntimeException: org.apache.lucene.store.LockObtainFailedException: Lock held by this virtual machine: C:\Users\vmishin\Documents\jbpm-server\jbpm-server-7.20.0.Final-dist\.index\MySpace\example-Mortgages\master\write.lock
at org.uberfire.ext.metadata.backend.lucene.index.directory.DirectoryLuceneIndex.<init>(DirectoryLuceneIndex.java:56)
at org.uberfire.ext.metadata.backend.lucene.index.directory.DirectoryType$2.newIndex(DirectoryType.java:74)
at org.uberfire.ext.metadata.backend.lucene.index.directory.DirectoryFactory.newCluster(DirectoryFactory.java:122)
at org.uberfire.ext.metadata.backend.lucene.index.LuceneIndexManager.indexOf(LuceneIndexManager.java:66)
at org.uberfire.ext.metadata.backend.lucene.index.LuceneIndexManager.indexOf(LuceneIndexManager.java:42)
at org.uberfire.ext.metadata.backend.lucene.provider.LuceneIndexProvider.index(LuceneIndexProvider.java:73)
at org.uberfire.ext.metadata.io.index.MetadataIndexEngine.doIndex(MetadataIndexEngine.java:157)
at org.uberfire.ext.metadata.io.index.MetadataIndexEngine.doAction(MetadataIndexEngine.java:136)
at java.util.ArrayList.forEach(ArrayList.java:1257)
at org.uberfire.ext.metadata.io.index.MetadataIndexEngine.doCommit(MetadataIndexEngine.java:256)
at org.uberfire.ext.metadata.io.index.MetadataIndexEngine.commit(MetadataIndexEngine.java:239)
at org.uberfire.ext.metadata.io.IndexerDispatcher$IndexerJob.get(IndexerDispatcher.java:189)
at org.uberfire.ext.metadata.io.IndexerDispatcher$IndexerJob.get(IndexerDispatcher.java:159)
at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1590)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.apache.lucene.store.LockObtainFailedException: Lock held by this virtual machine: C:\Users\vmishin\Documents\jbpm-server\jbpm-server-7.20.0.Final-dist\.index\MySpace\example-Mortgages\master\write.lock
at org.apache.lucene.store.NativeFSLockFactory.obtainFSLock(NativeFSLockFactory.java:127)
at org.apache.lucene.store.FSLockFactory.obtainLock(FSLockFactory.java:41)
at org.apache.lucene.store.BaseDirectory.obtainLock(BaseDirectory.java:45)
at org.apache.lucene.index.IndexWriter.<init>(IndexWriter.java:800)
at org.uberfire.ext.metadata.backend.lucene.index.directory.DirectoryLuceneIndex.<init>(DirectoryLuceneIndex.java:52)

That happens for previous versions as well.