I noticed that when you are in shipyard, ship gets a constant delay and can't finish after you walk out of the shipyard and wait on your ship until it's done. I observed that a really long time ago, I don't know if it still works like that.
If you're talking about shipyard there, I suggest walk away from the shipyard and wait more than one day. Any time you show up and stay on a shipyard, final production date gets a little delayed.
If it's not on shipyard it might be a bug. To be honest I don't know if same thing happens in factories.