I forgot to mention this earlier, but technology fails happen. You can’t avoid them, but you do need to prepare for them. Always check right after the interview call to see if your recording recorded and is complete. If you discover that your recording is static, or cuts out five minutes in, or isn’t there at all, don’t panic. Hopefully you took some notes while you were talking (if you don’t take notes during interviews, then you should start, or find someone to sit in on the call and take them for you); review them and see if you can fill in missing information from memory.
If you have no recording, no notes, and no recollection of what you talked about, then you’re going to have to bite the bullet and ask your customer to spare a few extra minutes to go over the questionnaire again. Hopefully, they’ll understand.