I was presented with a DVD containing plans for woodworking toys & projects, plus instructions to copy the same. No DVD apps, either copying or playing would recognise this DVD as such.
Only the Finder would show the DVD on the desktop. Drag & dropping of various folders was painfully slow, then stopped after only 130.8 MB of 2.69 GB had copied. This was after ten minutes.
Disk Utility on two High Sierra Macs wouldn't register it as a DVD.
However, DU on a Leopard PPC PowerBook does recognise it as a DVD in an optical drive, but even then, won't allow copying, it falls over after about 5 minutes.
It's all fucking bullshit.