After 17733 Build was installed my documents were deleted with the folder contents replaced by 'downloads'. I read a few posts and searched everywhere but nothing remained (I could tell by the remaining disk size that they were gone). I recovered them from my last backup but it took a good 8 hours. The next Build did exactly the same. This was too much, so after restoring them a second time I renamed the folder. Not had the problem again but that doesn't mean my action fixed the issue. I did check in case a new profile had been created but it wasn't that. If it happens again I think I will drop our of the Insider programme. One thing I don't understand is that there were two Document folders. The one surviving happened to be on One Drive whereas my meaningful stuff was under /users.