GSA 4163B burn problems

Having successfully burnt both DVD-R and DVD-RW for some time my unit now fails every time at the lead-in stage, writing the file titles but no contents. In the case of the DVD-RW it is the exact same media used successfully previously.

I have upgraded the firware from A102 to A105 but to no effect.

CD-R and CD-RW continue to be burned successfully.

Where is the best place to have the log analysed for clues as to the problem and its solution, please?