Position of the word ‘just’
Solution 1:
It's possible, but the first rebdering sounds more natural to me. "just probably" hints of being barely probable, or emphasizing that it's only probable, not certain; whereas "just hasn't" hints at "it's simply because he hasn't gotten around to it, not that he intentionally neglected to do it." That's the more likely sense, so the more likely construction. On the other hand, one could put it near the end: "He probably hasn't gotten around to it JUST yet". in which case one infers that he plans to inform the other person eventually, just not yet.