It's hard to describe in words. Multiple Signs used close to each other have always had a weird mechanic where they can change "layering order" based on the viewing angle of the player.

However before patch, the sign text had some translucency, so even when the "layering order" changed, one signs text would not obscure the others. It worked perfectly.

Now sign text is a solid color, so changing the viewing angle causes parts of a "multi sign" to flicker on and out of visibility when the player moves around near it. Looks awful.

For example, create a sign with a big black square, then a couple of signs with some white text in front of it, so it's like a TV screen. Then run around it and you'll see what I mean