It could happen that the disk from which the ISO has been created was present with a bad sector or something thus duplicated in the ISO. Some disks also have some kind of protection to prevent them from being copied directly but can be made into ISO files, and thus require to use a decrypter first then copy the contents from it instead of burning the ISO directly, whereby the use of a virtual drive to mount, a decrypter app to be able to copy/rip the files to a new folder then burn them to disk.
seapig commented: Thank you for taking the time to reply - extremely helpful +0