Although Apple's other new iPhone models have no such issues, some iPhone 12 mini owners have been complaining of lock screen sensitivity problems that appeared the first time they powered on their handsets. The problem has been reported on both Reddit and the MacRumors forums and Apple still has to come up with an answer.
https://www.notebookcheck.net/Trouble-in-paradise-Apple-iPhone-12-mini-plagued-by-touch-response-issues.504279.0.html
Interesting, I only heard of the green screen issue showing up in China on iP12 models, seemingly worse than before, but nowhere else.
I spent some time on the phone with an apple advisor, they acknowledged green/yellow tint issue and confirmed it is being investigated.
No estimate on resolution time nor on the exact nature of the problem yet.
Still not sur if I should keep my unit or return it...