I try to grind all the fat before starting the red meat. Keep it as cold as possible. I then mix the two together in the ratio of meat to fat that I want. Mix good, then grind thru the second time, together. If I have the time I'll temper the mixture in the freezer before the final grind.
I have the same grinder, and usually have no problems. Just keep it all cold as possible and go steady.
I worked in the meat processing as an Inspector and meat cutter for better than 30yrs.
Johnny/JAG