Copied from a report on Discord:

This is awkward. :'< I checked "Remote Storage" and linked my G2G account ingame without issue. But when I clicked on linking Epic too, instead of asking for my credentials it told me it needed to restart. And upon closing, Steam auto-unlocked 7 achievements. I thought it may be a leftover from pre-release plays somehow, except two of these seven are "Reach the Reactor with a minimal score of..." and. I never reached the Reactor ever before. Pretty sure watching twitch streams doesn't count, no matter how hard I'd been backseat playing from the chat