I have no idea what could cause this, but please take a look at the Spider-5K.
Last night I played this (bad) mech and I was wondering what I can survive.
I'm not kidding when saying an Atlas would have been killed!
About 3 minutes I ran around having only my internal structure, it flashed over and over again, so i WAS hit, but I survived.
Shure, some hits might be without power because of the maximal range of the weapons, but other mechs were inside about 150 meters.
Once I got legged, I died in less than a second.
Don't get me wrong, I love surviving

During this fight I also noticed strange flying missiles, they circled around me like some kind of moon, like my speed was too high for their turning-angle.