360 disc tray won't open when upright

always lay it flat. even if you just tap it when it's standing upright the disc can pop out of the tray and get scratched.

That is pretty much how it works. When the Disc is in the drive and being accessed, it's not sitting on the tray. If was sitting on the tray it would make a terrific noise would get scratched and wouldn't be being read anyway. It opens easier when there
is a disc in the tray due to the way the mechanism works in the drive. When there is no disc, I would assume the opening mechanism works differently.

Regardless of how it works, the drive has developed a fault, a pretty common one too. My spare Xbox 360 also has a similar issue, although sometimes the drive won't open even when there is a disc in there. On the spare machine I have solved the problem for
the moment by always keeping a disc in the machine. There is no risk to leaving your game in the drive.

If the issue gets worse, the only thing to do is send the machine for a repair.

Thank you for the information however it does not anwser my question very well. What I wanted to know was the cause for the xbox 360 disc drive getting stuck when opened upright but not sideways and a explanation for why a disc prevents the disc drive form getting stuck.

It flashes rapidly when the disc door opens or closes, since it won't open or close... I'd say you have a tray issue. Unfortunately, since you opened it, if there was a warranty, you just voided it.

oh yeah, forgot to add, my disc tray is also having a problem sometimes where when i try opening the disc tray, the power button flashes as normal but the disc tray doesn't open. it opens after the 2nd time trying.