Why wont some dvds play on my Blueray?

I recently bought a Phillips Blueray player and some of my bought dvds either wont play or will play but the picture jumps. Some of the dvds will play with no problems. Could anyone please help as it’s driving me mad and i cant watch any of my fave movies. Cheers. Sheep

What model Phillips? Could some of the movies be PAL format or heavily scratched?

Burned DVD’s that don’t play could be crap media i.e. poor burns.