Users are reporting that when they open the forum, they are signed in as someone else.
This is very common when the host is using session caching. If they have Varnish or Cloudflare installed it is currently set up incorrectly. The other issues are probably a knock on effect of that too.
Say I register, make 10 posts and leave.
You approve all 10
I'm still in the newly registered group until I come back to the site and my 'status' is re-assessed and then I will drop out of that group and become a normal user.