Oh I do still run things on mch so I don't fall out of shape completely. I think it's mainly just occasional mid-fight Wildfire fumbling. That and other little things compounding, like sometimes don't get the last Cooldown in overheat, sometimes might press an un-proc'd shot by accident, just silly stuff like that I guess. Here's my last MCH stream if you want to look it over:
https://www.twitch.tv/videos/279489659
(I changed to a 3-ammo opener and started blowing up turret for hypercharged Wildfires and it definitely increased my opener quite a bit and my overall dps by 200-300 from what I could tell)