Hello,
I managed to fix it.
I had to 1) deactivate the plugin, 2) delete the files from the server, and 3) delete all references to Events Manager in the table wp_options of the database.
After this, I reinstalled the plugin and everything worked out of the box.
From this experience, I believe it would be a good idea to make it easier to fully remove the plugin (mysql entries included).
I will mark this as solved, although the problem was neither identified nor satisfactorily solved.
Thanks for those who helped!