Unfortunately the CD32 has a proprietary CD-Drive. Nobody found a 3rd party replacement up to now.
4x times and Verbatim CD-R sounds good. Do your Backups work in WinUAE?
Do you have a friend that could do a backup for you? Maybe your burner is faulty, writes the first MB ok and then craps out.
Can you try your backups in another CD32, maybe the drive is worn out and you have to geat a replacement, don't fear they are around...maybe try cleaning the lens but watch out not to break it.