Could it be browser-dependent? (I’m on up-to-date FF52esr right now.)
Edit: Also, I have now verified that the error object “LW1 user detected, legacy salt attached” appears twice in the JS console (even for a single login submission), with different JS source references (although the data in the error object itself seem to be identical). So it may be that a LW1-style login is being attempted but is failing, either because some password data got corrupted on the LW2 side, or due to some client-side issue.
Could it be browser-dependent? (I’m on up-to-date FF52esr right now.)
Edit: Also, I have now verified that the error object “LW1 user detected, legacy salt attached” appears twice in the JS console (even for a single login submission), with different JS source references (although the data in the error object itself seem to be identical). So it may be that a LW1-style login is being attempted but is failing, either because some password data got corrupted on the LW2 side, or due to some client-side issue.