Mines are not removed by juggernauts, they just let them explode. Kinda what the real bomb disposal squad also does. Also yes when mines are placed behind walls the juggernauts will leap over the wall. This animation sometimes does not show correctly when they get shot etc etc. So no bugs here.
They are designed to take the hit, that's why they wear such good armor.. Eeerhm yeah that barrel.. I know they do seem to be doing some very important stuff after the mine has exploded. What they are doing exactly? I don't know cleaning up? Or maybe they are just dazed by the explosion. But we cannot categorize this as a bug as Midoki has responded a couple of hundreds times already about this question. (hint) Because they don't, that would render walls useless. Try using this knowledge to your advantage. Some players use this to trap juggernauts. Because they jump in to reach a mine, but they won't jump out. So they start destroying the wall. In the mean time you defenses can put those cannons to work.
I'm just giving you the information that already on the forum is. This is what the devs already have said about the juggernauts. You can go out and use the search funtion in the top right corner and you will find exactly the same info brought to you by devs. Also just tagging developers in your messages does not make them read your posts.
