roll back on incline & at very low speed makes a hard shift

My 2007 Lincoln MKX has 47,000 miles on it but has major issues with the transmission that worry me. First when backing into my garage on a very slight incline it will roll forward as soon as you take your foot off the brake. If you don't go from brake to gas really fast like a drag racer it will roll forward almost like it is is drive. 2nd problem is more worriesome. When driving very slow , like 5-10 mph in it like say a store parking lot or a cemetery it will suddenly make a loud banging sound & harsh shift. It sounds & feels like someone rear ended you or like the transmission is ready to fall off the vehicle. It does not do it consistently though. I have tried to mimic the low speed drive to make it do it but it will not do it all the time. Transmission fluid looks good & is at proper level on dip stick. What really baffles me is it is a FWD but the bang sound sounds like it is coming from the back on the vehicle & not the front or even from the center. Been trying to get as much info on this as possible & have read alot about transmission problems with this vehicle. I have read about others having these similar problems & wonder why there has not been a recall on them.