Well, I don't know what is going on here.
I never have to faff around with my 2400, it just works. I feed all heavyweight paper, these days mostly Harman Baryta, via the rear feeder, but I have fed loads of other stuff too, including the very heavy Hahnemule rag papers. I don't have to push down hard on the paper or maintain pressure on it for ages or anything like that. I just apply a gentle pressure until the printer tugs on it, then I go and do something else until my print is ready. I know I have printed hundreds of A4s and A3s now, and I think I might have had two or three misfeeds in that time.
John