If I disable a Datapack by using another Datapack Minecraft crashes.

If I disable a Datapack by using another Datapack Minecraft crashes, but if I do it manual with command it works and Minecraft don't crashes. I includet the function tahat crashes Minecraft.

---- Minecraft Crash Report ----
// Uh... Did I do that?

Time: 20.07.19 15:25
Description: Exception in server tick loop

java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
	at java.util.ArrayList$Itr.next(ArrayList.java:851)
	at rh.e(SourceFile:79)
	at net.minecraft.server.MinecraftServer.b(SourceFile:820)
	at net.minecraft.server.MinecraftServer.a(SourceFile:774)
	at eac.a(SourceFile:128)
	at net.minecraft.server.MinecraftServer.run(SourceFile:642)
	at java.lang.Thread.run(Thread.java:745)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- System Details --
Details:
	Minecraft Version: 1.14.4 Pre-Release 7
	Minecraft Version ID: 1.14.4-pre7
	Operating System: Windows 8.1 (amd64) version 6.3
	Java Version: 1.8.0_51, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 3504864944 bytes (3342 MB) / 4294967296 bytes (4096 MB) up to 4294967296 bytes (4096 MB)
	CPUs: 4
	JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx4G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
	Player Count: 1 / 8; [vl['Clashbestie'/3, l='1.14 survival datapack', x=16.48, y=4.00, z=4.46]]
	Data Packs: vanilla, file/ItemTeleport_5 (incompatible), file/NoBabyZombie_4 (incompatible), file/DatapackManager_6 (incompatible), file/DropFeed_3 (incompatible), file/SlimeCraft_1 (incompatible)
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.