I has a AST Premmia 4/66d, 486 66mhz, 16 meg of ram. It has an onboard mach32 with 1meg, but I noticed while playing DOS games where was significant screen tearing. I got a ET4000AX, but now there is artifacting/glitching in games. The most noticeable is in Commander Keen 4. In the overworld when moving on the Y axis is occurs, but if I press ESC to go to the menu then back to the game, it goes away until I move again in the Y axis.
This also occurs during gameplay, as in the first level you go up a small hill, then it occurs, or down in the pit.
In other games such as WarCraft there is only small glitching in the upper right hand corner.

I though maybe the RAM on the card was going bad, so I pulled half to bring it down to 512, issue persisted. Same when I swapped the RAM I just took out back in.

This also occurs when loading the DOS VESA driver for ET4000.

I have attached some images of what happens during Keen 4. I hope someone here can offer some recommendations of next steps to try, or if the card is a bust.

Thank you.