Hi Seb,
You could try the 8.0.2 with (old) kernel 3.14 build by vpeter.
I have an i4Pro and it has 'stutter/low framerate' issue with the 4.4 kernel. The vpeter build fixes this.
Also there is a thread somewhere that this build also fixes boot issues on some SolidRun CuBox's.
Cubox IMX6 problems with new kernel (4.??)
Cheers, Airell.