this took a while (I wonder what happened ;) but a dashboard is available now:

We also collected information about API errors; more details about that and the funnel analysis in general are available at

The situation haven't changed since June: upload attempts with Upload Wizard fail with an embarrassingly high frequency, with about one in three attempts being abandoned by the user.

The data is too numerous and too complex to just look at it and see what's the problem (also, maybe we are not even collecting the right kind of data), so we need to come up with hypotheses about the problem(s) and test them. As the people with the most experience about UploadWizard problems, your suggestions would be invaluably helpful.