Buttons link issue when drupal is in subdirectory

Thanks for reporting this, I'll look on this issue later this week.

Perhaps this issue is related with this other issue below:

https://www.drupal.org/project/google_calendar_service/issues/3432121 💬 Move all entity links under admin/ path? Active

I was able to reproduce this, I installed a Drupal instance in a subdirectory (http://subsite.ddev.site/maresmuseum/) and I can see the issue you saw.

1. In the http://subsite.ddev.site/maresmuseum/en/calendar/1/events page, the link of the button "Add Event" must go to http://subsite.ddev.site/maresmuseum/admin/calendar/1/event/add instead the link is http://subsite.ddev.site/admin/calendar/1/event/add

2. Same situation in the http://subsite.ddev.site/maresmuseum/en/calendar/events page , the "List Calendars" button should go to http://subsite.ddev.site/maresmuseum/admin/calendar , instead the button link is http://subsite.ddev.site/admin/calendar

I'll create a MR to address this.

I'm afraid I will need set this issue aside, I need to do a lot of changes in the module (changing links in the entity files, plugins, etc) and I'm afraid I'll break things up if I continue to work on this one. If anyone wants to take this, be my guest-