Just bought a SNES copy of FFIII/VI from a local game store.
About 50% of the time when i pop it in it has garbled graphics and colors.

What's weird is that if i press in and hold on the cart when i flip the system on it will work about 90% of the time vs 50%.
I cleaned the contacts on the cart and they look fine, but it's still giving me the issue. The cartridge does have that semi-bad cartridge rattle.
Is it possible the PCB is loose inside of the housing?

Also:
Copy of Mario RPG that i bought from the same store has a similar issue where it will only boot about 20% of the time if im not pressing down/back on the cart as i flip it on. Same with a copy of Yoshi's island i got from ebay.

Could it be my system? Other games work 100% fine.

Any suggestions would be awesome!

Thanks