Did it sometimes happen to others that air strikes and sometimes other weapons don't detonate on impact, but stop in front of terrain or worm, wait a few moments and then detonate?

this is due to the Ping or lag of your opponent :)

Yup, unfortunately this is due to lag. We are currently writing some more coding to combat this which we hope to have live soon. Obviously, we'll never be able to make it 100% perfect, but we hope to make it a lot more stable!