Critical bug? Characters sometimes break on spawn

Sometimes other player’s characters spawn ‘stiff’ on your client but on their client they aren’t
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Only logical reason would be that I use :ReplaceBodyPartR15() to replace each bodypart (including head) when a player spawns? I don’t think there is an other way of doing it. And I also disable RequiresNeck and the Dead State (on client) when using the function.
Also when this bug happens it also players the death sound?

If this is an engine bug can someone report it?

How are you turning players into R15?