RE: UP2414Q won't reliably resume from sleep or reboot using mDP to DP cable
So you have "1.2" mode selected in the Dell monitor settings menu? (Default setting is 1.1 - you get 3840x2160 but it's at 30hz)
Have you run successfully without the second monitor/card - just the UP2414Q at 1.2?
Does your system "sleep" or "hibernate"?
What were the issues you had earlier?
Thanks for any additional info.