You are welcome to do or not do suggestions here, as it's your computer and you will feel the consequences. However you should also be aware that frequently some Users have huge blind spots and assume they know more than they do, and/or the person trying to help them knows less than they really do.
My suggestion to run the job and drop the data somewhere other than the unreliable optical media was a good one as it isolates the cause of the problem to either "A" or "B" (optical drive and/or media, or the rest of the system). It's a valid troubleshooting method.
Also, if you are doing incremental backups (and not full backups) and you delete the original source data, you are probably going to get those errors, as incremental backups only "copy" data that actually changes, but a totally deleted source file doesn't "change", it disappears completely. I asked if all the missing data was pictures. Now I wonder if all the skipped data has a 1:1 correlation with the data that was deleted previously.
Also I reiterate your data backup solution is inadequate. In addition to being unreliable, you are spending time manually messing with it when, for the low cost of a good Hard Drive, the data backup operation could occur regularly and invisibly with no human involvement. In addition to the standard backup of just the data, you could also be performing image backups of the system drive as a safeguard against a time when either your system data is corrupted or destroyed beyond repair, or the system drive itself fails, which is inevitable.
Edited by hamluis, 01 June 2017 - 06:57 AM.