We need to know where your live. Not the exact address, but the region.
In some places in the world, any DVD disc would be recorded for a different standard. You need to eliminate that as being the issue.
About R/W disc recordings. This can vary a lot. A R/E dis is a very poor test for may system. A perfectly good DVD player might read a DVDS made yesterday, but not one made today.
What you need is a couple of brand new high quality DVD replacement drives for your machine. There has been a few instances when a OEM got a bunch to really bad DVD mechanisms. My guess is that a trend new DVD player will work fine on a disc mastered by a professional source. (A Sony pictures DVD movie.)
I have made lots of DIY copies of downloaded movies with near 20 per cent either failing or working poorly. Others have had similar results. It is the cheap hardware.
For a scientifically valid study , , you need about 25 players and 100 professional DVD movies. Expect the good drives to play 98 out of 100 DVDs. Did you do that?
Reference:
https://www.lifewire.com/best-sata-dvd-burners-832424This article implies tact there are some bad stuff out there and the user needs to stick with brand s that have got good reviews.