It looks like there are still sometimes Concurrent Modification Exceptions.
[Server] Craft Scheduler Thread - 1122/[WARN] [PowerBoard] Plugin PowerBoard v3.5.15 generated an exception while executing task 2818341
02.10 18:24:48 [Server] [INFO] java.util.ConcurrentModificationException: null
02.10 18:24:48 [Server] [INFO] at java.util.HashMap.computeIfAbsent(HashMap.java:1134) ~[?:?]
02.10 18:24:48 [Server] [INFO] at net.minecraft.scoreboard.Scoreboard.func_96529_a(SourceFile:82) ~[?:?]
02.10 18:24:48 [Server] [INFO] at org.bukkit.craftbukkit.v1_16_R3.scoreboard.CraftScore.setScore(CraftScore.java:58) ~[forge:?]
02.10 18:24:48 [Server] [INFO] at de.xite.scoreboard.modules.board.ScoreTitleUtils.setScore(ScoreTitleUtils.java:90) ~[?:?]
02.10 18:24:48 [Server] [INFO] at de.xite.scoreboard.modules.board.ScoreboardManager$2.run(ScoreboardManager.java:207) ~[?:?]
02.10 18:24:48 [Server] [INFO] at org.bukkit.craftbukkit.v1_16_R3.scheduler.CraftTask.run(CraftTask.java:82) ~[forge:?]
02.10 18:24:48 [Server] [INFO] at org.bukkit.craftbukkit.v1_16_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:54) [forge:?]
02.10 18:24:48 [Server] [INFO] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
02.10 18:24:48 [Server] [INFO] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
02.10 18:24:48 [Server] [INFO] at java.lang.Thread.run(Thread.java:829) [?:?]
02.10 18:24:48 [Server] Craft Scheduler Thread - 1167/[WARN] [PowerBoard] Plugin PowerBoard v3.5.15 generated an exception while executing task 2818349
02.10 18:24:48 [Server] [INFO] java.util.ConcurrentModificationException: null
02.10 18:24:48 [Server] [INFO] at java.util.HashMap.computeIfAbsent(HashMap.java:1134) ~[?:?]
02.10 18:24:48 [Server] [INFO] at net.minecraft.scoreboard.Scoreboard.func_96529_a(SourceFile:82) ~[?:?]
02.10 18:24:48 [Server] [INFO] at org.bukkit.craftbukkit.v1_16_R3.scoreboard.CraftScore.setScore(CraftScore.java:58) ~[forge:?]
02.10 18:24:48 [Server] [INFO] at de.xite.scoreboard.modules.board.ScoreTitleUtils.setScore(ScoreTitleUtils.java:90) ~[?:?]
02.10 18:24:48 [Server] [INFO] at de.xite.scoreboard.modules.board.ScoreboardManager$2.run(ScoreboardManager.java:207) ~[?:?]
02.10 18:24:48 [Server] [INFO] at org.bukkit.craftbukkit.v1_16_R3.scheduler.CraftTask.run(CraftTask.java:82) ~[forge:?]
02.10 18:24:48 [Server] [INFO] at org.bukkit.craftbukkit.v1_16_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:54) [forge:?]
02.10 18:24:48 [Server] [INFO] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
02.10 18:24:48 [Server] [INFO] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
02.10 18:24:52 [Server] [INFO] at java.lang.Thread.run(Thread.java:829) [?:?]