java.util.concurrent.CompletionException: java.util.ConcurrentModificationExceptionjava.util.concurrent.CompletionException: java.util.ConcurrentModificationException at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:273) ~[?:1.8.0_181] at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:280) ~[?:1.8.0_181] at java.util.concurrent.CompletableFuture$AsyncSupply.run$$$capture(CompletableFuture.java:1592) ~[?:1.8.0_181] at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java) ~[?:1.8.0_181] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[?:1.8.0_181] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[?:1.8.0_181] at java.lang.Thread.run(Thread.java:748) ~[?:1.8.0_181]Caused by: java.util.ConcurrentModificationException at org.apache.commons.collections4.map.AbstractLinkedMap$LinkIterator.nextEntry(AbstractLinkedMap.java:552) ~[commons-collections4-4.1.jar:4.1] at org.apache.commons.collections4.map.AbstractLinkedMap$KeySetIterator.next(AbstractLinkedMap.java:450) ~[commons-collections4-4.1.jar:4.1] at java.util.AbstractCollection.toArray(AbstractCollection.java:141) ~[?:1.8.0_181] at java.util.ArrayList.<init>(ArrayList.java:178) ~[?:1.8.0_181] at info.magnolia.periscope.rank.ml.IndexedBuffer.asList(IndexedBuffer.java:97) ~[magnolia-periscope-result-ranker-1.1-SNAPSHOT.jar:?] at info.magnolia.periscope.rank.ml.NeuralNetworkResultRanker.outputArrayToResults(NeuralNetworkResultRanker.java:193) ~[magnolia-periscope-result-ranker-1.1-SNAPSHOT.jar:?] at info.magnolia.periscope.rank.ml.NeuralNetworkResultRanker.rank(NeuralNetworkResultRanker.java:143) ~[magnolia-periscope-result-ranker-1.1-SNAPSHOT.jar:?] at info.magnolia.periscope.Periscope.fetchSupplierAwareSearchResults(Periscope.java:135) ~[magnolia-periscope-core-1.1-SNAPSHOT.jar:?] at info.magnolia.periscope.Periscope.lambda$search$0(Periscope.java:111) ~[magnolia-periscope-core-1.1-SNAPSHOT.jar:?] at info.magnolia.periscope.search.SearchRunner.lambda$execute$0(SearchRunner.java:85) ~[magnolia-periscope-core-1.1-SNAPSHOT.jar:?] at java.util.concurrent.CompletableFuture$AsyncSupply.run$$$capture(CompletableFuture.java:1590) ~[?:1.8.0_181] ... 4 more