Signs that were placed with a setblock command that doesn't specify the content of all lines are converted to completly blank signs when the world is reloaded. If you use pick block to get that type of sign, the item count goes negative when you place it. However when it's placed, it places a regular sign.
/setblock ~ ~1 ~ minecraft:standing_sign 0 replace {Text1:"{\"text\":\"This is a sign\"}"}/setblock ~ ~1 ~ minecraft:standing_sign 0 replace {Text1:"{\"text\":\"This is a sign\"}"}Also occurs with the fill command. Does not occur with blockdata.
Comments 3
Oh, I didn't realise. Still, the fact that it's even possible to get a bugged sign using vanilla commands qualifies as a bug.
There are a lot of reports concerning that already, but see Grum's comment on MC-87143:
It now only accepts proper json for each line and each line has to exist.
It will show as an empty sign otherwise.
you need to specify every line when setting the block