Meta Box

Thanks, that worked out for me!

But the topic is not solved! We need a solution for this error!

This issue is fixed in this commit a few months ago https://github.com/wpmetabox/meta-box-beaver-themer-integrator/commit/08a1db06918c6bcca77c7a8e01766dee76a7ee59

Can you please check if it is available in the plugin source code on your site?

Yes, it is in the plugin source code.
But the error is on line 142 ..!?

Hi, thats not a useful solution, because the events in that category change and you do not want to change the menu every time. In WordPress posts current page parent is highlighted why not in metabox custom post types? Within a category you should be able to view a post and the parent category is highlighted as current page or current category parent.