Hey Leaf, a few days back I got more information on it as I had him try again and the user was getting the mismatched token error. (same error as before).
And I poked around on the Git Hub and saw you commented (about a year ago) about this type of error, and you had said it was an intermittent thing. The user in question was someone using Chrome with Icognito. So that lead me to ask for browser info, and it turns out he was using Tor - so I suspected it was related. The issue was still listed as open.
Just adding to it if any of that helps ring a bell.