We're receiving this error, we had something similar which was caused by an outdated application which has since been removed.
Error: INSERT INTO `ibf_forums_forums` ( `parent_id`, `forums_bitoptions`, `position` ) VALUES ( '73', 0, 178 )
IPS\Db\Exception: Field 'topicrules_texto' doesn't have a default value (1364)
#0 /home2/<removed>/public_html/system/Db/Db.php(938): IPS\_Db->preparedQuery('/*<removed>_foru...', Array)
#1 /home2/<removed>/public_html/system/Patterns/ActiveRecord.php(487): IPS\_Db->insert('forums_forums', Array)
#2 /home2/<removed>/public_html/system/Node/Model.php(2494): IPS\Patterns\_ActiveRecord->save()
#3 /home2/<removed>/public_html/applications/forums/sources/Forum/Forum.php(1265): IPS\Node\_Model->save()
#4 /home2/<removed>/public_html/system/Node/Controller.php(419): IPS\forums\_Forum->formatFormValues(Array)
#5 /home2/<removed>/public_html/applications/forums/modules/admin/forums/forums.php(132): IPS\Node\_Controller->form()
#6 /home2/<removed>/public_html/system/Dispatcher/Controller.php(90): IPS\forums\modules\admin\forums\_forums->form()
#7 /home2/<removed>/public_html/system/Node/Controller.php(69): IPS\Dispatcher\_Controller->execute()
#8 /home2/<removed>/public_html/applications/forums/modules/admin/forums/forums.php(44): IPS\Node\_Controller->execute()
#9 /home2/<removed>/public_html/system/Dispatcher/Dispatcher.php(153): IPS\forums\modules\admin\forums\_forums->execute()
#10 /home2/<removed>/public_html/admin/index.php(13): IPS\_Dispatcher->run()
#11 {main}
Backtrace: #0 /home2/<removed>/public_html/init.php(1015): IPS\_Log::log('INSERT INTO `ib...', 'uncaught_except...')
#1 [internal function]: IPS\IPS::exceptionHandler(Object(IPS\Db\Exception))
#2 {main}
We now have this error. I believe this relates to another old app, which was topic rules going by the error? Unless, this is the topic rules that can be added to a sub-forum creation.