That looks like the KProbe log, and the disc was scanned at max speed (maybe 12x, if I had to guess).
The drive won't burn any slower than its minimum supported speed. If 2.4x is the lowest offered by the LiteOn for these Umedisc media, then that's what the discs were written at. Just information for future burning & an addendum to SJ's great advice and info.
We look forward to hearing of future success with different discs. :iagree:
BTW: yes, errors at 50% are probably a result of a failed layer jump.