Glitched building parts?

Hello everyone. The last update has fixed some annoying bugs (ragdolls especially), but has apparently brought some more.
I’m currently playing on the Redsnow UK server, and have built a small house in the mountains. But for some reasons, a friend who joined me told me he couldn’t get up the stairs because a wall was blocking him. He couldn’t damage or remove said wall, and there was no wall for me. To him, I was just casually walking through a wall.
A couple hours later, we were exploring the map, and I saw a twig triangle foundation on the beach. I tried to destroy it, but couldn’t. And, as you have maybe guessed, my friend didn’t see it, and for him I was just floating a couple feet into the air.

Anyone has experienced this issue too?

TL,DR: I see building parts that my friend doesn’t see, and he sees some I don’t see.

This bug has been around since at least last patch. It wasn’t introduced with today’s patch.

On my server there are some floor that I can walk on and other players don’t see and pass through them.

I think this has been around for at least 3 maybe 4 patches, not sure what causes it though.