How to reproduce:
1. Execute a command with string tags like that:
2. Put this command into /setblock command:
You will get a command like that:
3. Try to execute the /setblock command. It will conflict because one string tag overlaps another one.
It'll be better if command like /setcommand exists; this command should set a command into a command block on spicified coords. It will be so useful for mapmakers.