Adding a list of failed subtitle synchronizations
To alert the user that those subs might need a closer look. It could be placed in the "History" tab and potentially have a button to blacklist the sub and search for another one, or an option to retry the sync/manually adjust the time if needed.
Although just having the list of failed syncs with a hyperlink to the specific Movie/Series page would also accomplish the same result since you can just do all of those actions on their specific pages too.