Make SURE it ACTUALLY is a Mini 2[emoji15]! Not going to go into detail or point fingers, but depending where you bought it, it very well maybe a refurbished or returned product. More importantly it's all about the "Chip and Retina Display". As mentioned, "A7chipset or better" and would suggest in the General Settings to "Enable Hardware Decode"..
As future reference when purchasing apple products make certain your product is authentic. Go to settings, General, and click ABOUT! Model Number, Serial Number and other information are readily available. Problem with resale or refurbished is the possibility of NOT having what is specified on the box or detailed descriptions... Just throwing this out there as this HAPPENS in speedy sales.. Just throwing caution to the WIND[emoji6]