magic 3 weird behaviour

For many years, I used magic 2 modchip without any prob, only it can't boot with Gameshark, recently I upgraded the chip, in one of the local store, to magic 3, now it can boot with gameshark with only one strange problem, everytime I boot the CD format game, it failed to boot, unless I put it in vertical position, but to boot a DVD format game, I must put it in horizontal position, if it in vertical position, it won't boot, the prob isn't annoying at first though, I just have to put it in vertical position, if I want to boot GS and change it into horizontal position afterwards to boot dvd game, but now after I installed my HDD, this prob annoys me as the machine weigh become heavier, I recall the first time this problem occurs, is when I put the unit in vertical position for the first time.

sounds like your laser

but the DVD games loads fine in the horizontal pos, and even quicker than other new unit