So a couple days ago my app stared wigging out on me, and started showing strange upgrade offers that would appear and disappear and then it would drop entire segments of my trips and I'd have to call and manually have them added back. But all of this led to me taking screen shots of everything and getting Delta to honor the prices which got upgrades to delta one on ATL-ICN RT for $600 and ATL-KEF RT $400 both were Main cabin X fares that normally didn't allow for paid upgrades.
So thank you delta for still not having a competent IT team and having a wonderful customer service team