I've been having the same issue, and I remember exactly when it started. I was in the boar processing factory (the one that's a duplex with the mutant corn place) with the big mutant boar in the cave below the basement. I walked down through the tunnel and chopped all the breakaway boards that you might typically fall through so I could see what was below. I shot the boar a lot, then as I was rounding the hole to line up another shot, I had to slightly climb up the side next to a corner (so I wouldn't fall into the hole). That somehow pushed me up through the ground, and I found myself stuck inside of a block beneath the floor of the duplex building but above the ground. I pickaxed my way out of the blocks as much as I could, but after a few chops I got injured somehow. I got a broken bone. Then I kept chopping and I ended up dying. Once I spawned back in, buildings started having phantom blocks. I've never had them before this experience, but now I see it everywhere.
I have an i7-7700HQ with 16Gb of RAM and GTX 1060 with 6Gb of RAM. Running Windows 10 64bit. I'm running the current update (19.1).
