I agree with everyone.
During some light readings about DVD, I remember reading that drives fail before discs; the lifespan of the average DVD player was 6 months to 3 years. My USD$ 40 ones live about a year, and my iBook’s DVD reader failed in 3 years. If the discs were written using new drives, perhaps newer drives will read them.
Just to complete the thread, I should mention that I buy only Taiyo Yuden DVD-R or Verbatim DVD+R (for LightScribe) from reliable internet stores, when on sale. Though DVD-RW can be rewritten a thousand or so times, one imprint (glass) will last only about 6 months (when it recrystallizes). The earlier supposedly have lifespans in the hundreds of years; but remember: DVDs are translucent, and must be kept from light and diurnal temperature changes (for their medium isn’t perfectly elastic).
Given their inability to be recognized by three drives, I too don’t think your errors are random (‘stochastic’). Changes in design (specifications), manufacturer, firmware, operating system, and age all affect the ability of a drive to read DVDs (which one engineer called ‘miraculous’ in itself). Less expensive dyes (recognizable by color & lustre) decay at quite variable rates. Sometimes this is on purpose (as with Mr Phelps’s tape recordings).
The above is just to supplement the excellent advice already given by others.
I’ve not examined the source code for ‘ddrescue’ (which is available), but I should imagine the worst it would do is spin your drive for a shorter length of time than watching it (which is at 1x). I’ve never experienced any problems watching several DVDs in a row on my television.
However, I agree with everyone that a failure of the first (innermost) track to be readable on three machines is not likely a random problem; and you should try other machines and look at other factors first. (Some television recorders install copy protection when recording programs from National Geographic & other channels, which would require ripping before copying.)
PS. I do have a great heat problem writing from newer laptops, expecially those thin ones with ‘bleeding edge’ circuit board design. I’ve installed a free program that reads sensors, and set it to ring when the CPU or hard disk begins to increase its temperature rapidly. Then I shut off all other programs, screen savers, &c, and place an ice pack in a towel under the laptop before burning. When the bell rings, the ice has melted, and I substitute another. I’ve been able to burn for hours without a flaw at 18x in this manner.