User blog comment:DaNASCAT/Technical Update: October 3, 2016/@comment-28398720-20161006114222/@comment-126761-20161008021251

Update 2: additional tweaks have been made in the past few hours that should improve matters further.

It has been a little complex to nail down - only affecting some users some of the time. The issue appears to be that some requests have been misdirected to servers that don't accept updates (hence errors on attempting to submit changes), which we've been working on resolving.