I tried the same thing out on a another site: http://www.ekudden.org .
This is a new WP installation, with only two plug-ins, that comes automatically with the WP-installation (Akismet and Hello Dolly). These are not activated.
I installed "Events Manager 5.2.1" and performed a minimum of settings.
I then created Event_test_1 that was only published once and it worked OK as expected.
I Created Event_test_2 the same way, but after publishing I performed a change of teh scheduling - I prolonged it a month. And then I checked the result.
It turned out that everything seems to work OK on this site.
Does anyone have an idea on what may causing the error on the failing site?
The plug-ins that are installed on that site is:
Akismet - active
Batch Cat - active
Events Manager - active (of course)
Fast Secure Contact Form - active
Fullscreen HTML editor - active
Get Post List With Thumbnails - active
Hello Dolley - inactive
HTML import 2 - active
Mass Page Remover - active
Post List - inactive
Redirection - active
SI CAPTCHA Anti-Spam - active
User Access Manager - active
Vice Versa - active
W4 Post list - inactive
WP Events Calendar - inactive
WP Login - active
WP Mobile Detector - active
WPtap Mobile Detector - inactive
XCloner - active
Is it possible that any of these plug-ins can have an impact on Events Manager? I am not so familar with WP-coding structure can name-conflicts for funtions be an issue. I Tried WP Events Calendar first, but then I found Events Manager that did the job I needed. Can WP Events Calendar (although it is inactivated) cause the problem?