When you use "/setblock" to set a sign, you may be getting a "An unexpected error occurred trying to execute that command" error in the chat, this error basicly has no reason to appear. The text specified in the command is set and visible, other Text<number> compenents are also set automatically. No error in the game log. Makes no difference if you use the new method with ' or normal " and \".

Command: /setblock ~ ~ ~ minecraft:oak_sign{Text1:"

"}

Why is this happening?
Beacuse the NBT Text2, Text3, Text4 are missing, basicly if one Text<number> component is missing.

On which blocks?
On all wall sign variants and all normal standing sign variants.

Note: This bug is appearing since 18w43a, but not in 1.13.2, because signs have changed in this snapshot the bug may exist because changes made for the introduction of the new sign variants.