There seems to be a glitch with my Tonka era SMS, where it sometimes repeats part of the sprite data regarding certain sprites. Some trace might be broken, I don't know.
What's the question?
Knowing there's a glitch doesn't help us what's causing it. If you know it's a broken trace then it should be easy to repair. Sounds like a WRAM problem to me though. Might have to replace it.
Screenshots would help though!
I think this is a good example of the problem
(http://i.imgur.com/Vj33clg.jpg)
on which basis is it reproducible? per the whole system with any game inserted or just per certain amount of cartridges?
it might be access speed degradation of particular IC inside of system/cartridges.
It happens with Marksman Shooting & Trap Shooting, where the scores of the targets I hit also also look weird, as I can only see part of them.
More specifically, it happens with the Marksman Shooting part.
You sure it's not a VRAM issue? That would be way more likely than the VDP itself being bad.
I think it is.