When you have a calendar view created from template. When you use the pagination, the tabs no longer work.
E.g. you go to your calendar/day page and go to the next day. The URL shift to /calendar/day/20170409. This means the tabs are also formed similarly. E.g. /calendar/month/20170409 for the month tab. This URL doesn't work, because the month expects something like /calendar/month/201704
Changing the contextual filters so e.g. the month display uses the full date, makes sure not the entire month is shown.
This seems related to behaviour in core where arguments are added to the tabs when using them, so unsure on how to fix this.
1.0
Code
The change is currently missing an automated test that fails when run with the original code, and succeeds when the bug has been fixed.
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
Patch #23 fixed it for me. It works by altering the local tasks and removing extra arguments from the path. Maybe we should check in the css changes separately if those aren't necessary for this.