I thought at first this was some setting I had wrong in "Build" or possibly some other problem like trying to do something across sim borders. But it's not. And now tenants are reporting this to me, too.  And yes, on sim edges (this used to happen ages ago) but I'm finding it all over as well. Like, I put out something and I can't see it. No, it's not that it has a transparent back (so many mesh things do). It's just not visible, even being a prim block. No, it doesn't re-app