I have a Atari 800XL that is having trouble recognizing game cartridges some of the time.

By that I mean that every second or third time I plug in a game cartridge, it goes to either the BASIC screen or the self-test screen.

If I press down on the left side (logo side) of the top of the machine, it usually manages to recognize cartridges fine. As soon as I stop pressing, the graphics become garbled.

Does anyone have an idea of what's wrong with this machine or how to fix it?

Thanks!