I do not think there is an issue on 2014 X3
I have a '14 X3 with Premium Hi-Fi (the more expensive of the two choices avail. In the US).
I have played one DVD movie (commercially recorded) one time for a short time...essentially to confirm that it worked. I do not recall any problems with either controls or sound levels.
When I get a chance I will give it a more thorough test.
Our BMW: '14 X3 35i, Deep Sea Blue, Black Nevada Leather, Fineline Wave Wood, Satin Aluminum Roof Rails, Premium Pkg, Cold Weather Pkg, Navigation System, Driver Assistance Pkg with ALL them cameras, Premium Sound
Our truck: '03 Ford F350, 7.3L turbo-diesel, 4WD, Lariat package, Lear topper, cow catcher, Blue over Grey (Go Rice!)
"Old Faithful's just a fountain compared to the glory of true love" -- John Prine