use "/data merge" on a sign crash minecraft.

Hello.
I explain badly, If you need more information ask me

Use "/data merge block" on a sign cause a crash.:

Internal Exception io.netty.hander.codec.DecoderExecption: h: Loading NBT Data

To reproduce :

1. Place a sign
2. Use a /data merge block on sign
   Exemple :

   /data merge block ~ ~ ~ {Text3:"{\"text\":\"Test\",\"bold\":true,\"italic\":true,\"color\":\"dark_green\"}"}

   3. made several times /data merge on a sign.
   4. Look at the difference with "/data get block"