I've done a lot of googling, and I've found a few threads here and there that talk about this, but there's never an answer for it, and it doesn't seem that anyone ever confirms that YES, it's a bug, or NO, it's a client issue with GPU memory or if it's just settings that need to be adjusted.
I'm playing on A19, on a multiplayer server (I do not own the server). I run an i5 8600, 16 gb RAM, GeForce RTX 2060 Super. Settings have been optimized using GeForce Experience, but generally hover around ULTRA settings. LOD is set to 100. All of my drivers are up to date.
Some POIs I have encountered have phantom blocks that you can walk right through. Wooden planks that don't disappear when broken, and lots of strange marble-like textures scattered around the building. You (and zombies) can walk through them, but they obstruct vision. A lot of the textures in the POI also flicker, as if two textures are on top of one another.
Nobody else on the server has reported seeing this issue, but we may not be looking at the same POIs in the same area. It seems to go away *sometimes* if you leave the game and reload some time later. Leaving the game and coming right back in doesn't seem to make it disappear. In fact, I'm not sure there's any rhyme or reason as to when/why it goes away and comes back.
edit: I've attached some photos of the glitch. This is the gas station where I've set up a temporary sleeping spot. The first picture shows a bunch of extra, phantom blocks in front of the door and windows.
The second picture shows the gas pumps that have turned into phantom blocks.
The third shows the gate to the backyard (looks like a giant block of gate textures), some of the phantom marble on the windows and side walls of the station, and a pile of trash
outside looks like a black and white checkered box.