When placing a sign with or editing a sign to have JSON text components, advanced text components that require resolving to retrieve and display data do not resolve. This includes selector, score and nbt.

How to reproduce:

/setblock ~ ~ ~ minecraft:birch_sign{front_text:{messages:['{"selector":"@a"}','""','""','""']}}

Observed behavior:

The sign shows @a

Expected behavior:

The sign shows names of players in the world