I've also had it happen to me before, but not recently.
I have an alt, using normal login. This account uses Google login under a different e-mail. However, a few years ago the forums got the two mixed up for some reason (when I used my login credentials for the one I got logged into the other), which someone had to fix for me. There's even a thread about it somewhere here. I suspect it had something to do with logging in from the same IP/device.
I always assumed the issue I, and now @Captain, experienced had something to do with this, since IIRC this issue popped up after I recently logged into my alt.