Please see the attached chair structure.
[media]It consists of an upside down stair, an opened trapdoor attached to the back, and a sign on the side.
When loaded in 1.13-pre10, the chair loses its sign - it pops off and falls to the ground.
MC-133880
"Chair" Structures Bordering on Edge of Chunk Lose Their Signs
Resolved
Invalid
0
md_5
Confirmed
Minecraft 1.13-pre10
Retrieved
The sign-block is not attached to anything so it would be completely valid for it to break.