JEM 3 giving 404 errors on events

I see this changed to JEM 2.2 but we had done a lot of custom styling when it was in beta as 3.07. We haven't dared change it due to all the customization. Now for some reason some of the newer events are going to a 404 page even though there seems to be no difference from the ones that are working. The categories exist. Events are attached.
Joomla version 3.6.2

Anyone have any ideas what's causing this and how to fix? It's not even on all of them, just the latest added.

Hi, I can't help, but are you really on Joomla! 3.6.2 because there is a Joomla! 3.6.4 stable!
What do you mean with " events are attached". I don't see any attachments.
EDIT: please look:
developer.joomla.org/security-centre/660-20161002-core-elevated-privileges.html

I meant they are attached to the category. It has not been updated to 3.6.4 yet.



Also I tried to delete/recreate category to test and am getting this error when trying to adjust settings:
Save failed with the following error: exception 'UnexpectedValueException' with message 'JemTableCategories::moveByReference(1, last-child, 109) parenting to child.' in public_html/libraries/joomla/table/nested.php:334 Stack trace: #0 public_html/libraries/joomla/table/nested.php(825): JTableNested->moveByReference('1', 'last-child', 109) #1 public_html/administrator/components/com_jem/tables/categories.php(219): JTableNested->store(false) #2 public_html/administrator/components/com_jem/models/category.php(299): JemTableCategories->store() #3 public_html/libraries/legacy/controller/form.php(734): JemModelCategory->save(Array) #4 public_html/libraries/legacy/controller/legacy.php(702): JControllerForm->save() #5 public_html/administrator/components/com_jem/jem.php(42): JControllerLegacy->execute('apply') #6 public_html/libraries/cms/component/helper.php(405): require_once('...') #7 public_html/libraries/cms/component/helper.php(380): JComponentHelper::executeComponent('...') #8 public_html/libraries/cms/application/administrator.php(98): JComponentHelper::renderComponent('com_jem') #9 public_html/libraries/cms/application/administrator.php(152): JApplicationAdministrator->dispatch() #10 public_html/libraries/cms/application/cms.php(257): JApplicationAdministrator->doExecute() #11 public_html/administrator/index.php(51): JApplicationCms->execute() #12 {main}

I finally got it to stop showing that and most of the categories show but one is particularly stubborn. I see no difference either in the admin area or the database between that and the ones working.