Husks can attack Amplifiers through walls if the wall is right next to the amplifier on the second level (Where is doesn't force you to build in a + shape and only the small box around the top). The pictured D amplifier was destroyed without the walls ever being touched.

Posted Aug 14, 2017, 7:59 PM UTC
are you sure it wasn't lobbers? I usually cap amplifiers like this and havent had any issues
Yes there's a metal roof, you can see the edges of it hanging over the walls.
I'm not sure about amplifiers but I have had this happen to me with the bluglo siphons, so I can see it being a problem with amplifiers as well.