I find this very puzzling and would be interested in other’s opinions.
I have backup of several movies.
My son has two DVD players where they work fine.
I have three players, on two they don’t work at all.
On one a wintel they do.
To make it even more puzzling.
On two different PCs the DVD reader could not read them.
I haven’t mentioned specifics, as I am just interested in the principle of some stand alone players working, others not, and pcs unable to play them.