Default [Q] HDMI scaling problem since 4.2?!

I have a Sony Xperia Tablet Z (1920x1200). With original 4.1.2 it would correctly scale the picture to 1920x1080 when connected to my TV with MHL/HDMI-adaptor. Since 4.2 and now with 4.3 update it will not change the resolution and displays a squeezed 1920x1200 picture on my TV. So the aspect ratio is corrupt, making wide faces etc. when watching photos or movies.

Sony says that it is Google's fault.

The Xperia Tablet Z has a hidden service menu where I can change the HDMI resolution but it is set as 1920x1080 as standard, and changing this to 720p does not correct the aspect ratio issue.

I have bought the app Screen Settings from Forbitel, and I have also tried other resolution changer apps, since I am rooted and have Busy box installed.

I am able to change resolution to 1920x1080, which displays correctly at my Tablet Z (it leaves 120 pixels unused =black bars at top and bottom) BUT when connected to my TV it will still only display a squeezed 1920x1200 picture on TV screen!

Why has Google removed the scaling from 4.2 when it was working perfect in 4.1.2?

Any information regarding this or ideas how to fix it would be much appriciated! Thanks!