I've noticed, I have to keep chain tighter than normal, and tighten it more often; but I also noticed I was tending to "pinch the bar" when cutting overhead, like you mentioned; caused more issues.

Are you creating a slight "undercut" slot, before you throw the chainsaw bar on TOP of limb, to finish the majority of the cut? (less chance of a bind, when you get close to the last part of cut)

FYI: I put a Y62 Powercare 18" chain and bar kit, on one of my M18 saws and it does use more oil, but seems to work fine. (Home Depot) $32