I have been having trouble lately with a lot of duplicate tabs appearing, but I see that the behavior of the pinned tabs has changed 
.
In my case, I often hit Open Daily Note button when a pinned tab is in focus, and end up opening several daily notes for the day, and since I have also pinned the task aggregation page with the tasks plugin, when I jump to each task page from there, I also end up mass producing tabs.
I hope the past behavior will be optionally selectable. At the very least, I hope it will no longer open duplicates if the linked file has already been opened.