We do not offer support for custom code here, so this may not be something we can fully troubleshoot – however, I’m curious, how are you generating the /en/ version of your events post?
If it is with a third-party translation plugin, then we unfortunately do not know how that plugin goes about generating the /en/ version of the events post, and your best option here would be to contact that translation plugin’s support teams for more information on doing this.