No matter what I do, I can't create more than 26 events in CiviEvent. It seems this might have happened in the latest CiviCRM update because I already have more than 26 events, but only 26 are visible in the dashboard.
I created a fresh install of Joomla 3.7.2 and CiviCRM 4.17.19, then imported in my civicrm_event table with around 100 events and the problem still exists.
I removed all the events from the table except 25 of them. Then I was able to create one more event. After that, I only got this error when trying to create or duplicate an event:
If I delete an event, I can create a new one up to 26 (no matter the ID). If I import 100 events into the civicrm_event table, only 26 of them will appear on the dashboard. If I delete one of the visible events, one of the "invisible" ones will appear.
I have a test site set up and can share access if someone can take a look at it.