The is an ongoing recurring issue and a real pain.
When I open the "show-tasks" and click on a link beside a task, sometimes the link takes me to the task in the Pull Request and sometimes it simply closes the modal window and stays at the top of the PR page.
When I look in the source the id of the task the link points to is a completely different number to the task id itself.
Source code for the link
You can see the link is pointing to #task-79473089.
Source code for the task
You can see the id for the task is task-2657163. They don't match so the link goes nowhere.