I'm not sure if this applies to the 500x series, but from my experience with the 5045, I never had an issue finalising any DVD-R/RW, Video CD-R/RW or DVD+R discs when filled to the brim where it would show "Disc Full". DVD-RWs prepared with long initialisation and DVD+RWs cannot be finalised and if I attempt to do this, I get "Change Disc".
I did however encounter an issue with recording an Audio CD-R to the brim, as it kept on recording beyond the 80 minute mark. :rolleyes: When I stopped the recording after it clocked up about 110 minutes, it actually wrote 79 minutes 57 seconds of audio on the disc. However, even in this case it still finalised the disc successfully.
If you have not updated the firmware on your DVD recorder before, I would recommend doing this. If you don't mind using a few DVD-Rs or DVD+Rs for testing (including one of those that failed to finalise with your first burn), you could try filling two or three different brands with any recording (such as from a terrestrial TV channel) and leave the recording run until the disc runs out of space. Then try finalising these. If all fail, then it may be an issue with the laser recording at the outer edge of the disc. If one or more fails including another one of those that failed with your first burn, then the failures may be caused by the LiteOn not properly detecting the capacity of the disc, i.e. calculating more free space than what is actually available.