Howdy Johan,
I am sorry to hear your permalinks need to be flushed each update. That is likely the result of a third party plugin. The Events Calendar by itself should never the rewrites flushed, but some third party plugins might do strange things when the update, such as flushing the rules before the rest of the plugins have loaded. At that time any plugin which has not loaded but has it’s own permalinks will suffer glitches, ours included.
You could try flushing permalinks on plugin update. From what I have read the action “activated_plugin” should fire when a plugin does a regular update, so in theory this line of code would flush the permalinks each time a plugin is updated:
add_action( 'activated_plugin', 'flush_rewrite_rules' );
I can not really test out that theory since none of our tests sites have the conflict yours does. If the above is not helping for some reason you might try this:
add_action( 'init', 'flush_rewrite_rules', 100 );
That will flush the permalinks on each page load. This will make your site run a bit slower, but you never face this issue again.
Does that all make sense? Will that work for you? Please let me know.
Cheers!
– Brook