Broken tile problem with Famicom

[boye]

I have a problem with my Famicom, where a seemingly random set of tiles gets replaced with another seemingly random (but consistent on a per-game basis) tile that appears to be a pattern. Here's an example and other examples with other games.
Super Mario USA: Hill gets replaced with broken tiles.. (See photo)
Super Mario Bros. The beginning of a level has some broken tiles.
Super Mario Bros 3: When you fly up to the top of the level, you see the broken tiles.
I have more Famicom games, but the problem does not happen on any of my other games.

[MWK]

Try cleaning the cart really well.

[boye]

It happens with multiple games, so I'm not sure if it's the carts.

[P]

Then the cartridge connector in the Famicom may need to be cleaned.

Sounds like the nametable (tile map memory part of the Video-RAM) gets partly corrupted.

[boye]

Should I use the credit-card method to clean it?

[P]

Yes as long as you find some way to scrub the pins in there without deforming them, and clean them off with isopropyl alcohol and let it dry completely.
Cartridges may need cleaning as well.

[Sydsydsyd]

In my experience, games showing glitches / weird behaviour are related to bad contact between socket and cartridge pins.
Some times solved cleaning both socket and cartridge. In other cases, i've seen a lot of games with cutted tracks by the case wearing pcb on top of pins.