Sometimes, when trying to load filament into the feeder on the AMS Lite, it won’t go in. It’s like trying to push it into a wall. If I keep trying, it eventually works just fine. It doesn’t seem to be isolated to one port. I’ve tried varying pressure on the button to no avail.
Got me stumped. 
Make sure the end of the filament is cut cleanly and that the filament is reasonably straight that you’re pushing in. it definitely can be a bit challenging at times but seems to become easier with practice. Also, if you “miss” on inserting the filament properly it can actually push up in the wrong area and out the top of the feeder. So try keep filament centered and inserted slowly.
Yeah, happens to me now and again. Sometimes, just “spinning” the filament a bit helps, changes the angle. Or just, “feeling around” with the end. Sometimes I have to re-cut the end.
I experienced the same problem. It seems like wherever the filament is being directed there is not enough slope on the receiving path to guide it smoothly. I notice a similar issue on the hot end. It has caused loading to fail once. Otherwise, can workaround it. This is after using the printhead to cut, so it’s not user error.