Some help?

Hi,

I just got a Dreamcast second hand on ebay. There's an issue that I'm having and I'm trying to diagnose because there's not really any consistency to it?

Got 20ish games and the majority run with zero issue. Pop in disc, game loads. Easy.

However...a couple of games are extremely temperamental (Tomb Raider: The Last Revelation and Worms: Armageddon). They boot rarely; but the odds of it booting do increase with the console tilted.

I also have a spotless copy of Crazy Taxi, but I've only got it to load to menu with the Dreamcast on its back. I'm not sure if the GD-Rom is dying, if there's issues with those individual games for whatever reason or if my laser might need a clean. It's just really odd because the condition of the disc doesn't seem to matter? A very 'loved' version of Shenmue came with it that I honestly wasn't sure would boot in a 27 year old console; but worked every time I've loaded it.

Anyhow, any thoughts, advice, suggestions would be highly appreciated :)