Any time I log out of a world any sign with a clickable command gets erased. This includes wall signs and standing signs. The text and command get cleared leaving just a blank sign.
Linked issues
Comments
/setblock ~ ~1 ~ minecraft:standing_sign 0 replace {Text1:"{\"text\":\"Test\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/say Test\"}}"}

Duplicates of MC-87143
As grum said :
It now only accepts proper json for each line and each line has to exist. It will show as an empty sign otherwise.
Please provide the command you used to obtain the sign.