Please respect our forum rules and do not corsspost. One thread is sufficient. The error at 85% suggests some sort of error with the burner itself. Have you checked to see if Sony offers any firmware updates? Have you tried lens cleaning? Is the burn time (at least, up to the 85% point) still the same as before? If so and if the things suggested don't help, your drive may be dying a premature death, which is not too uncommon for the more delicate laptop drives; contact Sony support about possibly a replacement.
Matshita drives are a pain to crack (they in fact go above and beyond the specified behavior for a RPC Phase II drive), and unfortunately, there is no region-free solution at the moment, and there is a good chance that there won't ever be one.