After investigating I can confirm that the update created thousands upon thousands of duplicate entries for each individual event that already existed in our calendar. This would explain why the OP above also suffered an Allowed memory size issue.
Whatever was done in the update seems to have created masses of unnecessary data, which most basic hosting will not be able to handle.
I am currently trying to delete it all from my server. We’re starting again with another plugin and manually moving valid data over to it, because I do not think any future update of this plugin is going to be able to clean up the mess it has created on my server.
