The official position is that there was no foul play, but I still can't believe in this time of super-heightened cyber-security concerns, anyone in the Democratic party would try and use a smartphone app for anything election related. The whole platform (IMHO) is compromised when you're talking nation-state level adversaries, let alone when your opponent is the Commander-in-Chief of the NSA/CIA, the ones who we all know put the back doors in place to begin with.
Occams razor though - in 2016 Bernie got gypped and lobbied for a new process. Half a case of beer says that as soon as they have a proper accountability, it comes to light that nobody really has any clue how the system is supposed to work.