Sign can't be written

When a Sign is placed, I can't write on it. Except, when it's the first sign placed after starting the game.

When I want to write on another sign (after writing on the first one since starting Minecraft) it won't let me. I also can't leave the window to write on the sign (will attach screenshot) by pressing escape; only by clicking the mouse outside of the sign.

 

How to reproduce:

1. Place first Sign and write something (will work)
2. Place another Sign and try writing (won't work)