Why does my Game Boy Advance Sp have a difficult time reading games?

I recently bought a used GBA SP on eBay for a decent price. I got the exact console pictured and the system powers on and shows the Gameboy logo just fine. However, when I insert any cartridge it either won’t load it at all or it will be a glitchy mess. One exception to this is when I insert my Pokemon LeafGreen copy and hold it in tight with my hand it will load and play properly as long as pressure is being applied to the cartridge. But as soon as I release the pressure it will freeze or glitch out, the same with all the other games. I have tried cleaning the contacts with 90% isopropyl alcohol and compressed air from a can on the console and the cartridges to no avail. What else can I do to repair this? It seems like it should be an easy fix.