I upgraded to the latest version today. Immediately I got errors running the website, and the site would not load. It seems that a zapcalendar plugin was crashing. I reinstalled and everything worked. A few hours later, the site was down again. This time even the backend of the site was down for managing extensions. The directories for zapcalendar in both the administrator and components directories were missing. I deleted the directories for zapcalendar in the plugins directory including the subdirectory in the content plugin directory in order to get the website to run again. Using the update function for extensions, I was able to remove the remaining links to zapcalendar. I reinstalled, and everything seems to work.
What is going on!