Suppose one such probe malfunctioned or was damaged, what would the results be if it crashlanded on a lifeless primordial planet? This probe must be capable of some degree of self-replication. It might not actually diminish the possibility that some out-of-control self-replicating system comes back to destroy you. (Worse, you've explicitly designed it to replicate systems that cause barely discriminate destruction.) How much might you change before it no longer recognizes you?