If you experience sudden split-second image stretching in 1920x1080 mode:
Please use a file manager that has access to System Partition (for example - Root Essentials). In /system/ folder find build.prop file. Find parameter ro.hwc.sysrsl and set it to 9. Save the file and reboot the device using Tauon Power Manager.
After this action the error should not occur.
It is highly recommended to have active cooling installed to use 1920x1080 mode.