I'm stuck on this same issue. Burned 34 of 35 discs (20 minutes) each - THEN FAILED TO WRITE on disc 35.
Left with option of ejectiing - won't eject. Force ejection displays message total set will be unuseable.
Suspect it is because I turned off "verification" as it was taking over 1 hour per disc.
I agree with you that this is a MAJOR DESIGN FLAW. Causes days of lost labor and discs.
Their TECH SUPPORT number " 1-866-279-7694 ext 2; then 5; then 1 (for Toast 7) said their system was down and they could not even give me paid support. I ran into this before with Toast 6 and upgraded to Toast 7 to get the spanning capability. I am afraid that if I try again - using the verification that the results will be the same. LOSS of over 35 hours straignt time and 35 more discs. Can't get anyone to address the issue.