punch out cart sprite corruption

[paulb_nl]

I have received a Punch out famicom cart but I am seeing some sprite corruption. With a cold boot it works fine but after a few mins the corruption gradually comes in. It starts with a few pixels then they get bigger and its always the same sprites. It stays that way unless I turn it off for a while.

Is it possible this is caused by a faulty capacitor in the cart? Or is one of the chips damaged?

Here are some pictures:

[thomas83lin]

I had a Zelda 1 with messed up graphics turned out it was the CHR ram chip

[Diskover]

I have a The Flintstones that happens the same but only in the title screen and in the intro.