DVD drive - problem with double-sided disks

Since I'm disabled-retired and usually have a lot of free time, I like watching DVD movies (mostly bought from Amazon, since they've got good selection and even free shipping is usually delivered next working day).

About a year ago, I noticed that double-sided disks tend to acquire a visible narrow ring on the upper surface near the outer edge which typically makes that portion more or less unreadable (that was a Samsung drive). I replaced the drive with an LG one because the older one was starting to also have problems recognizing that there was a disk in the drive.

I'm now starting to get the same markings using the LG drive, which seems highly unusual considering it's a totally unrelated drive (or I presume so -- maybe they're identical and there's a licensing agreement involved?). The implication is that something is improperly contacting the upper surface -- no problem at all with single-sided disks, because of the label.

Any ideas what I (or more likely, my shop, which never heard of this problem before) should be looking for?

A related question, on buying from Amazon ... first thing I'll check when interested in double (or multiple) features is whether they're on separate disks. The Warner "4 Film Favorites" releases are a great buy, but are always on 2 double-sided disks. Is there any way to get Amazon to add to their published specs, when multiple movies are on one disk, whether it's dual-layer (which I have no problem with) or double-sided?

Many thanks for any help that can be offered.