Player is unable to speak to Qel'Thuzad (error in console)

[Punkred]

I have a player who is unable to receive any quests through Qel'Thuzad in the adventure guild. This is the error that is generated when he tries to use the NPC:

[12:23:43 WARN]: [EliteMobs] Task #24376 for EliteMobs v8.5.4 generated an exception
java.lang.IndexOutOfBoundsException: Index 10 out of bounds for length 10
at jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64) ~[?:?]
at jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70) ~[?:?]
at jdk.internal.util.Preconditions.checkIndex(Preconditions.java:266) ~[?:?]
at java.util.Objects.checkIndex(Objects.java:361) ~[?:?]
at java.util.ArrayList.get(ArrayList.java:427) ~[?:?]
at com.magmaguy.elitemobs.quests.menus.QuestInventoryMenu.generateInventoryQuestDirectory(QuestInventoryMenu.java:51) ~[EliteMobs.jar:?]
at com.magmaguy.elitemobs.quests.menus.QuestInventoryMenu.generateInventoryQuestEntries(QuestInventoryMenu.java:38) ~[EliteMobs.jar:?]
at com.magmaguy.elitemobs.quests.menus.QuestMenu.generateQuestMenu(QuestMenu.java:46) ~[EliteMobs.jar:?]
at com.magmaguy.elitemobs.quests.menus.QuestMenu.generateDynamicQuestMenu(QuestMenu.java:41) ~[EliteMobs.jar:?]
at com.magmaguy.elitemobs.quests.QuestInteractionHandler.processDynamicQuests(QuestInteractionHandler.java:31) ~[EliteMobs.jar:?]
at com.magmaguy.elitemobs.npcs.NPCInteractions$4.run(NPCInteractions.java:86) ~[EliteMobs.jar:?]
at org.bukkit.craftbukkit.v1_20_R1.scheduler.CraftTask.run(CraftTask.java:101) ~[paper-1.20.1.jar:git-Paper-49]
at org.bukkit.craftbukkit.v1_20_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:480) ~[paper-1.20.1.jar:git-Paper-49]
at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1480) ~[paper-1.20.1.jar:git-Paper-49]
at net.minecraft.server.dedicated.DedicatedServer.tickChildren(DedicatedServer.java:447) ~[paper-1.20.1.jar:git-Paper-49]
at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1394) ~[paper-1.20.1.jar:git-Paper-49]
at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1171) ~[paper-1.20.1.jar:git-Paper-49]
at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:318) ~[paper-1.20.1.jar:git-Paper-49]
at java.lang.Thread.run(Thread.java:833) ~[?:?]