The 2nd egg spawning is likely due to the lack of dps on Data Core #2. I’m not sure if you just right-clicked on the Data Core, instead of stutter stepping forward so that you prevent the need for the units at the back from walking around to the sides.
Another would be you didn’t queue up after the egg kill to hit the Data Core because it is roughly the same time that you need to start loading up Medivacs at Data Core #1 to quickly fly to next drop off point. The recommended would be once everyone is dps-ing the egg, to queue up a movement command somewhere near Data Core #2 and queue up an attack command on it.
================================================================================
[UPDATE]
I have tested it out.
- You have 31 secs (in-game secs) after killing the first egg to kill Data Core #2 (which will take about 19 secs, factoring in killing of broodlings and 2x lings that come after).
- Failing which, a second egg will start spawning and will hatch in 24 secs.
- It only takes about 9 secs to kill an egg.
In each case, I am assuming you are using stim rines (at least 50% of the time) and haven’t lost any dps unit (losing the medivac is fine).
So yes, killing the second egg is more than feasible if you made a mistake. If anyone doesn’t know why the second egg is the issue, then I’d suggest that you read back the first post to better understand why this achievement must be done this way.