Jay, we have been over this quite thoroughly over the past few weeks & we seem to be repeating the same answers to you.
So I'll try & summarise.
There are 2 things here.
One is the quality of the burn , which as you've got a Benq 1620, you can check with CD/DVD Speed, under disk quality check. This you have been doing. If you get a result of 90% or better then you've got a good burn. And as you are using quality media deteriation should not occur. This percentage figure is an arbitary figure which does not represent how much of the data has been successfully copied but tells you , in CD Speeds estimation, how good the burn was. Note here that this is not stating how much of the data was successfully copied.
The other factor is whether the data was copied 100% in the first place. For that you need the original on HDD and compare that with what's on the CD/DVD. CD Check along with the other software I've suggested are 100% accurate in their comparisons and you get a pass or fail result, not 98% or whatever. Without the original data this is not an option.
You must think in these totally separate terms.
At this stage all you can do is the scan & hope for a good result.
With the files that are blocking etc this could be because of a media problem , bad burn/deteriation etc as the playing app cannot handle read errors. If you can successfully copy the file back to the HDD , try playing it & you'll probably find that the blocking is no longer present. This indicates a media issue which scanning should identify.