When worldborder is set in the "death zone" and your spawn chunks are in it none of the spawn chunks will load, breaking all redstone/command blocks.

Example:

You have /setworldspawn at 5000, 120, 0
do a clock at those coordinates (simple hopper clock) and output a comparator and a command block doing "say hi".
Check to see if you're spammed "[@] hi",
If yes, go to 0, 120, 0 then do these commands:
/worldborder center 0 0
/worldborder set 1000

Watch that after 10 seconds your "[@] hi"'s will stop and the chunks are no longer loaded.