Any guidance on restoring custom fields so they don't go away again?

This is becoming a pain, but a few years ago all my custom fields disappeared, leaving only Title, Description, Email, Phone, Facebook, Twitter and Yelp. Important stuff like all address related fields have gone away again. The last time I just scrapped the listings, recreated the listing setups and entered the data.

Anyone have an idea what causes this and how to end this issue for good? This issue just kills the value of this theme. The directory information is important, but so are other aspects of a local biz directory, but darn if every time I log in, I am fixing something.