I had the same problem, thinking it was an alignment problem between the alignment pin(screw) on the riser and the alignment hole in the limb.
What I found on mine was the small screw that holds the spring-loaded latch in place on the riser was not screwed in far enough. I backed the screw out all the way, lubed it with wax, and screwed it back in just enough that the limb would now seat. Hope this works for yours, keep us posted.