Steps to Reproduce:
1) Use the load.mcfunction file in a datapack on a server to summon a mob with a high number of characters (I'm having problems trying to upload folders on the report)
2) After running /reload, you will die with the client side death message as "killed by even more magic" whereas, in chat, there will be an error shown.

Error in chat: "Can't deliver chat message, check server logs: ..."

This error is shown in chat whenever any message fails to send due to the packet length. This is also seen when trying to teleport this mob to the player or running /data get entity on it. This shouldn't apply to the death message.

Expected Result:
The same death message appears in chat with a hover event.

Video