It's in the browser too, and it happens when you have only incoming raids (maybe blocks too, I don't know).

Until they fix it, a simple workaround is to have other units travelling. Have someone send you reinforcements or you send some reinforcements (1 Marauder will suffice for either) to a friend or your own block or even just a nearby inactive haven. While they are travelling, your "Underway" tab of the Stronghold should show you everything, including the incoming attacks.

You can even just recall 1 unit from your harbour, which'll give you 15 secs. For longer observations, do what I described above.

I hope this helps.