Please use https://open.vanillaforums.com/categories/off-topic for testing. You can select which category to post in when creating a new discussion https://open.vanillaforums.com/post/discussion
Do you have index.php in your forum url? If so enable pretty urls https://open.vanillaforums.com/discussion/comment/220157/#Comment_220157 Not sure whether it is related to your issue but pretty url have been a requirement for years but is not enabled per default. Plenty of issues from not having it enabled.
In the discussion list view, a sunk discussion displays the time for the last comment which was made before the discussion was sunk. They should show the time for the most recent comment made, even after the discussion was sunk.