Just tried creating a new feature in the AdminCP (previously I was doing so in the front end). I got an error, see below. When I hit 'back' on the browser, I had the new feature and only one, not multiple, but I did have the error below.
INSERT INTO `core_follow` ( ) VALUES ()
IPS\Db\Exception: Duplicate entry '' for key 'PRIMARY' (1062)
#0 /home/xxx/public_html/system/Db/Db.php(937): IPS\_Db->preparedQuery('/*IPS\\links\\_Ca...', Array)
#1 /home/xxx/public_html/system/Content/ClubContainer.php(144): IPS\_Db->insert('core_follow', Array)
#2 /home/xxx/public_html/applications/core/modules/admin/clubs/clubs.php(462): IPS\links\_Category->saveClubForm(Object(IPS\Member\Club), Array)
#3 /home/xxx/public_html/system/Dispatcher/Controller.php(85): IPS\core\modules\admin\clubs\_clubs->nodeForm()
#4 /home/xxx/public_html/applications/core/modules/admin/clubs/clubs.php(33): IPS\Dispatcher\_Controller->execute()
#5 /home/xxx/public_html/system/Dispatcher/Dispatcher.php(152): IPS\core\modules\admin\clubs\_clubs->execute()
#6 /home/xxx/public_html/admin/index.php(14): IPS\_Dispatcher->run()
#7 {main}