Repeatedly citing same item of personal communication The APA style indicates that personal communication should be cited in the format "J. Doe (personal communication, M dd, yyyy)" in-text, without a bibliographic entry. I was wondering what the best solution to citing such an item repeatedly is?

Example:


  J. Doe (personal communication, August 21, 2017) proposes that concept
  X is inherently meaningless without mechanism Y.
  
  [...]
  
  Doe (2012, 2015, 2016) presents mechanism Y in terms a, b, c. We could therefore
  assume that this predicts concept X to exist independently of Y,
  nothwithstanding J. Doe's (personal communication, August 21, 2017)
  objection that doing so would lead to undesired behaviour Z---it is
  what strictly follows from the system proposed in Doe (2012, 2015,
  2016).


Is there a better way to refer to the same personal communication the second time? Options like J. Doe (op. cit.), J. Doe (ibid.) etc. seem to not really work semantically (given what kind of object op. cit. and ibid. refer to) and be potentially ambiguous with Doe (2012, 2015, 2016), although I suppose the initial of the first name here may disambiguate.

Are there any established ways of dealing with this elegantly?

[Edit:] I should add that I have to refer to a different instance of personal communication with Doe elsewhere, so simply citing "Doe (p.c.)" later on would be potentially ambiguous, unless it somehow only referred to the most recently cited instance of personal communication.

[Edit 2:] To provide some context, we're talking here about a situation where the papers by Doe (2012, 2015, 2016) outline a particular theory but leave some aspect of it poorly defined or ambiguous. The private communication entails asking Doe for clarification as to how he intended that ambiguous aspect of the theory to be understood/implemented. So this is not really about relying on data or sources that are unavailable, it is about giving fair shrift to Doe's theory, and making clear as a starting point both for my own work and others how the original point was intended. If this is not taken into account there's a real danger of just attacking a self-made straw man here, and neither Doe nor I nor others in the field would probably be happy with that. It seems inevitable to me that full disclosure here entails citing the personal communication on more than one occasion, namely whenever Doe's disambiguating communication comes into play.
Without knowing the context, what you are trying to do seems poor practice to me. "This is important because person X said so in private" is impossible for peer reviewers to verify, and hence not authorative when written in a paper.