Main changes between V28 and v29 are faster routing algorithm, slight changes to the dynamic routing and small bug fixes.

Mine is running v29 and a backup (+ speed cameras) without any problems.

I think that is has more to do with the age of the MK4 unit itself, as to whether it will run a backup or not, mine is a 2006.

I always use a quality dvd (bulkpaq, 16x, Rytech dye) and always write at x2 speed, yes, you can write faster, but (to me) writing slower reduces the possibility of picking up errors, which is what causes the Nav crashes.

I did write a disc at x16 speed once (to test) and although it wrote the disc and reported no errors, it did crash my drive, so for me slower is better.

Same goes for the OS updates, I always write at single speed.

Try writing the backups at the slowest possible speed and see what happens, so it takes a bit longer but so what, if it works, right...

Hope this helps

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Sept 03, M3, Silver Grey. Retro-fits: Modded Mk4 DVD Drive, OEM Bluetooth, VR Control, Rainbow Speaker Upgrade, Sony SOT Amp, HK Sub, CCFL, Intravee II, NightMode.