I have this weird bug everytime I log into Joomla with a non-administrative user. Every time the user logs into the site, he is removed out of all Joomla user groups, except the Registered group. I also opened up the Joomla administrative console in a different browser, and assigned the user back to those groups, but every page visit (after the non-admin user is logged in) it removes him out of the group again. Logging out does the same. I'm at a loss after spending several hours on this, trying to figure out what is happening here.
The only thing that has changed to make this happen is upgrading the server to PHP 7.3.8 and Apache to 2.4. I'm doubtful as to whether that is the cause of the problem, but you never know.
Also, another piece of information, the user is only not removed from groups when he also is a part of the super user group. This makes me think that there is some condition that first checks for super users and then does some logic. I've disabled two plugins related to adding/removing from groups, thinking it was a bug with either, but I can still replicate the issue.
Furthermore, I've added in debug statements to the
JUserHelper::removeUserFromGroup function, but those are not even called when the user is taken out of the group!