I have a Ming Aralia and it has issues with dropping leaves as well; upon doing some research I found that this is a common problem with these plants. They will drop leaves cyclically and with even some mild change to their environment. In fact, mine loss all of it's leaves during the winter months indoors even though it's conditions were relatively unchanged other than the shorter daylight hours. Once spring came it started into growth again and has been doing well outdoors on my shaded porch once the warm weather arrived. I'm assuming it will defoliate again, when I bring it back inside.
I have found they do like a moist but well draining soil, indirect bright light and some humidity. Despite its issues, I do like this plant! The Parsley Aralia is attractive as well, I haven't seen it offered here.
Good luck with your plant!
