This has been happening a few times now. Sometimes in arena, when the opponent pulls out their non-backfire drone, they loose some hp.
Like just then, I was in rank 10 arena... someone pulled out their maxed Tonto and lost 60 hp.
I used to think it was just a glitch like sometimes when you die from an energy drain attack and the next mech's energy looks like it's missing a chunk, but that doesn't seem to be the case here since the numbers don't add up.
And... here is the video. I block off the names for privacy, but just know that the one with the divine tonto is me. and the video goes pretty quick.
Glitch happens on 00:13.
SM_glitch1.mp4