NeoGeo Hyper 64 Sprite Errors - Broken VRAM?

[maxisoft2]

Dear fellow arcadees,

I have lately been cleaning up my arcade collection and while trying one of my two NEO GEO Hyper 64 boards I experienced a wierd glitch (no matter which game is inserted). If I insert the game carts in my second ("back-up") HNG64 MoBo, they run just fine. I first suspected the slot pins to be bad / bent, but they are all looking fine. The pins on the game carts are fine, too. Systems tests all go through fine, however the scroll ram tests shows "N.U" instead of "O.K" (I figured that might mean something like "not used" in these fighting games I have?)
https://i.imgsafe.org/f99720fa0f.jpg
https://i.imgsafe.org/f99729dbe0.jpg
https://i.imgsafe.org/f9973b50c9.jpg
https://i.imgsafe.org/f9974758e0.jpg
https://i.imgsafe.org/f997539c1a.jpg

Maybe one of you has already experienced a similar error and knows about a fix? My suspection is that some of the cartdridge pins can't make a good connection - or maybe the VRAM is broken?

Best!
- Max

[Asayuki]

It could be a RAM issue, but it actually looks a more like bad addressing of the ROM bank related to a particular layer.