I'm still seeing this in 3.6.46 ESS. It only started 2 updates ago, perhaps? About a week ago, anyway.
The first export will work fine, but if I try and export to the same place again then it will give the error and not complete the export. Deleting the files before exporting solves the problem, but it is an unnecessary step that wasn't needed a couple of weeks ago.
It'd be great if you could look into it!