If an entity had been removed and it's ID taken by some other entity, clients who hadn't received a message about the removal and the new entity would end up reading ENTITY_POSITION messages for the new entity incorrectly. Reading an incorrect number of bits from the message would also prevent the clients from reading the rest of the data in the packet properly.
Now the server doesn't send position updates to clients during midround syncing (because there's no guarantee they know about the entity yet). Clients also force the read position to the correct place after reading a position update in case something goes wrong when reading the msg.
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