Problem/Bug My server keeps crashing

I'd appreciate any help I can get on this. Thanks!
Here's the crash log:
24.03 19:58:02 [Server] Server thread/ERROR Cause of unexpected exception was

24.03 19:58:02 [Server] INFO java.lang.UnsupportedOperationException: null

24.03 19:58:02 [Server] INFO at com.boydti.fawe.bukkit.adapter.DelegateLock.isHeldByCurrentThread(DelegateLock.java:81) ~[?:?]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.DataPaletteBlock.a(SourceFile:40) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.DataPaletteBlock.onResize(SourceFile:92) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.DataPaletteLinear.a(SourceFile:44) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.DataPaletteBlock.a(SourceFile:122) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.DataPaletteBlock.setBlock(SourceFile:112) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.ChunkSection.setType(SourceFile:60) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.ChunkSection.setType(SourceFile:54) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.Chunk.setType(Chunk.java:268) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.World.setTypeAndData(World.java:222) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.FluidTypeFlowing.a(FluidTypeFlowing.java:486) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.Fluid.a(SourceFile:69) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.WorldServer.a(WorldServer.java:590) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.TickListServer.b(TickListServer.java:82) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.WorldServer.doTick(WorldServer.java:313) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.MinecraftServer.b(MinecraftServer.java:1082) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.DedicatedServer.b(DedicatedServer.java:406) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.MinecraftServer.a(MinecraftServer.java:984) ~[spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:824) [spigot-1.15.2.jar:git-Spigot-a03b1fd-fc318cc]

24.03 19:58:02 [Server] INFO at java.lang.Thread.run(Thread.java:748) [?:1.8.0_191]

24.03 19:58:02 [Server] Server thread/ERROR This crash report has been saved to: /./crash-reports/crash-2020-03-24_19.58.02-server.txt