Sim invisible except for the Plumbob?

Do not save lived in houses to the bin. Yes, they cause corruption. Played lots have remaining data of Sims left in them. No per se a Sim but left over data, that's why if you find or build a house save a clean copy to the bin before playing it. That way you will always have a clean copy and not a played copy. If it were me, I would take at all custom content and start putting back a little at a time to see what type of cc is causing the problem. It's nine times out of ten custom content.

I would also clean out my bodyshop (bad projects) etc. if you have been working in bodyshop. That also causes problems. I would delete the cache files because they get too bloated and left over wrong data. I would move the Sim to a different house in case it is lot corruption then bulldoze the house.