Burn Failed

Hi, hoping for some insight here.

I’m attempting to burn a DVD ISO disk using Nero Ultra 6 onto a DVD-R
The content I’m wanting on disk is a bunch of folders. Inside these folders are anywhere from 0-100 *wav files (Conversations recorded by our phone system)

The burn fails every time.
Question: Should I choose Multi session or not?
any other thoughts as to why it might fail?

Thank you