Problem: if players get teleported on server side, they still might keep sending moving packets, resulting in very big moves occasionally, due to the moving packets not containing information about where the player moved from.

Suggested approach in short: How about adding a sequence number to moves - increase with teleports and special location changes, keep with normal moving - moving packets from the client with wrong sequence number are ignored. Note that the server controls/tells the sequence number except maybe right after login.

Extra features: The sequence number could be used to let the client tell when it has loaded (and rendered) the chunk which the player is standing on. (needs magic)