A-Jumping and A-Stuttering

[Slartibartfast]

I have set up my Phatbox in an Audi RS4 of 2001 vintage, with Navi Plus satnav. It doesn't seem to care about selecting a head unit from the selection menu, any of them seems to work, is this supposed to happen?

I permanently get random jumps and stutters and flickering track counter displays, maybe 2 or 3 per track, could this be bad comms between head unit and PB? Does anyone else get this?

Also, a few tracks are reported as 'corrupt track' but seem OK when looked at in the cradle on my PC, any ideas?

Ta very much!