I'm using no LVC with the 9918 of mine. I didn't even use a 6s with it. I've used 11 cells in a T4 with this controller and I really didn't like it that much. It even glitches once you're car have taken some distance from you.

I would say that is a bec problem, try using a ubec or rx pack, also with a combo of interference somewhere for the distance issue.

I've torn that dude apart just to make use of its heatsink. I got it from FDM without its case even. I really didn't like it alot when I put it through some harsh speedruns, but its surely one tough esc.