I'm having the same problem on a brand new, clean installation running under WAMP on Windows 10. I can create single and repeating events but the description does not get saved. I have also tried toggling multi-category events but this makes no difference.
PHP Version : 7.0.0
MySQL Version : 5.7.9
Server Information : Windows NT DEREKS-LAPTOP 10.0 build 14372 (Windows 10) AMD64
Fix jQuery? : Yes
Load JEvents Bootstrap CSS? : Yes
Max Input Vars ? : 2500
Club code set? : No
User Agent : Mozilla/5.0 (Windows NT 10.0; WOW64; rv:47.0) Gecko/20100101 Firefox/47.0
Joomla : 3.6.0
component_com_jevents : 3.4.13
module_mod_jevents_cal : 3.4.13
module_mod_jevents_custom : 3.4.13
module_mod_jevents_filter : 3.4.13
module_mod_jevents_latest : 3.4.13
module_mod_jevents_legend : 3.4.13
module_mod_jevents_switchview : 3.4.13
plugin_content_jevents : 3.4.13
plugin_finder_jevents : 3.4.13 (not enabled)
plugin_search_eventsearch : 3.4.13
plugin_system_gwejson : 3.4.13
I have not tried updating the event description via phpMyAdmin as I haven't found the right field yet (hint, please <!-- s:!: --><img src="{SMILIES_PATH}/icon_exclaim.gif" alt=":!:" title="Exclamation" /><!-- s:!: --> ) but I'm anticipating that it is not getting saved.
I'll be watching this thread with interest as it'll probably be the same problem/resolution. If you need any more information let me know.