Follow this template except for feature requests. Use pastebin when providing /protocol dump and any relevant errors.

Make sure you've done the following:

• You're using the latest build for your server version
• This isn't an issue caused by another plugin
• You've checked for duplicate issues
• You didn't use /reload

I am using PacketWrapper, however the error comes from a method that belongs to this library so I think it should be appropriate to put this here. The problematic code is the following:

MinecraftReflection.getMinecraftClass("EnumPlayerTeleportFlags","PacketPlayOutPosition$EnumPlayerTeleportFlags")

When this is run, it throws the following error:

Caused by: java.lang.RuntimeException: Unable to find EnumPlayerTeleportFlags (PacketPlayOutPosition$EnumPlayerTeleportFlags)
	at com.comphenix.protocol.utility.MinecraftReflection.getMinecraftClass(MinecraftReflection.java:2143) ~[ProtocolLib(5).jar:?]

I don't see the issue your tbh. The class does not exists and it throws an exception because of that. Maybe you should use the obfuscated name instead?