If you're an avid trader, all you can really do is to clear your void and have others clear their void before coming to your island. Clearing a void just means going to another village with 10 Residents while you have a full 10 residents in your town as well. If you are seeking to buy villagers from others, it's best to be "traditional" and just use NMTs or the campsite until this glitch is patched up!