DarienDragon

In our case I'm certain it's a host issue. Or more specifically, being the host is exacerbating the issue. But we're not on a server, one of us is creating the game and the other joining it. We have to restart whenever the host starts to get too visually bugged. In your case, since nobody's machine is doing double duty as host... maybe it's just taking longer to happen? On our end the client may not be playing long enough to see the phantom blocks by the time the host is. In which case, if we go back to it being purely a memory leak... then hosting a server seems to exponentially increase said leak. Which would also mean that changing all the video options in the world won't help (and that seems to be the case). Sadness. But it's the price of experimental I suppose.

After some testing I can confirm it's the same here. The problem seems to be the host, we transferred the saves to my system and suddenly I was the one with the graphical artifacts. Also worth noting; I have 4G of VRAM and 16 of system RAM, my VRAM shot up over 50% and my system RAM was at 90% load. I'm inclined to agree now that it's not GPU specific, and that a memory leak (somehow specific to the host) is the culprit. I don't know about the OP, but we have the same problem with the terrain quality at medium. I'll try dropping it to low tomorrow and report any changes.

This is exactly the problem my wife is experiencing. Also on a Geforce. It never happened before A19 though. It doesn't seem to be happening to me. I think it cropped up once on my laptop then stopped. I have a mobile Quadro K5000 card so it could be something about Geforce, as mentioned above? I don't have a solution (yet) but I figure something out I'll share.