All connectors in robots are likely to come loose... ive lost fights in the past because ec5's have come loose, and deans, and andersons etc etc.... i put a cable tie around them all now, not had a problem since... and bullet connectors on brushless motors i put some tape around.

The answer to the link poping out is having a link door that pushes on the "loop" of wire on the link... so it physically cant pop out without the door coming off...