The bug

Having a sign displaying a score of a nonexistent entity will cause the sign to corrupt random nearby tile entities and make them invisible when the user exits and reenters the world.

How to reproduce

1. Place multiple signs with text on them, and other various tile entities
2. Run the following command on any sign:

   /blockdata X Y Z {Text3:"{\"score\":{\"objective\":\"a\",\"name\":\"@e[name=Error]\"}}"}

   1.13: /data merge block X Y Z {Text3:"{\"score\":{\"objective\":\"a\",\"name\":\"@e[name=Error]\"}}"}

3. Exit and reenter the world to see multiple tile entities have become invisible

Code analysis

Based on 1.11.2 decompiled using MCP 9.35 rc1

The problem is that the client tries to process the score component by calling the method net.minecraft.util.text.TextComponentUtils.processComponent(ICommandSender, ITextComponent, Entity). This method should only be called by the server because the client has no access to the scoreboard or all entities.

This could also be fixed by replacing a processed score component with a text component containing the score.