Well, your event #7 is wrong. It doesn't affect one infected cell, it affects all currently infected cells, restarting Sine for all of them, changing scale back and forth...
If you want every infected cell to shrink over time, use Timer behavior, or Sine/LiteTween (with a long period time). But you need to do for one created instance, not for all instances at once. You can start the timer in event 5 and 6, immediately after spawning the infected cell. No need for a separate event #7.