After three summers, I can say for sure that of the three times that the antlion spawned, he only gave a warning twice on the first summer.
The other two times he spawned me and my friend were on the base and things simply started crumbling under us.
Also the second and only time he gave a warning on the first summer, the sinkholes appeared in less than 10 seconds, giving us no time to leave the base.
Is this a bug or the antlion doesn't always give warnings? The warning happening less than 10 seconds before the sinkhole is a normal behavior?
Regards