Placing creepers inside a base while being outside wall

[SrGlaucus]

We have walls in all directions that are 4-5 blocks thick and people from outside, especially blackpython6 and HmoYT, are currently managing to place from outside creepers inside our own base while bypassing all obby walls and making our chests explode. They even attepted to kill me with spawning creepers in our base while them being outside.

How am I suppose to report this since I can't printscreen the act itself. It would just appear as a creeper standing. And why has this server such a crap def that enemies can bypass walls from more than 5 blocks away and still spawn creepereggs in our base while them being outside in water?

 

[SrGlaucus]

To give you an idea of our walls:

First wall sand, behind it self generating walls, behind that obby wall of 2 thick in all directions. They were at least 4 blocks away from the inside of our vault while still managing to place ceggs inside our vault. The walls are not damaged.

Creeper explotions inside our vault, placed by, in this case, HmoYT from outside our walls:
I WOULD HAVE ADD IMAGES HERE, BUT DUE THE LACK OF 1 LIKE IM APPEARANTLY NOT ALLOWED!!!