Comets are known to break apart sometimes. Not all the pieces travel together................
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Well, there WAS Shoemaker-Levy 9, that broke apart, and the pieces of it hit Jupiter, back in 1994.
Jupiter’s extreme gravity tore it apart, but the pieces strung out and hit Jupiter at different times and locations.
Also, a comet’s trajectory could be altered by the force of the jets of material streaming out at odd angles................