Upgrading water mill from level 3 to 4 taking forever

It was last Friday that I decided to upgrade my little water mill, which is supposed to take 24 hours. Now, a week later, it's still at 58%. It's upgrading, but sloooooowly. It seems it is upgrading only while I am logged on, and taking a break when I'm not online. Surely this is not how it is supposed to be?

I should perhaps add that I had to go away last weekend, and could not log on again until Monday. Several processes had halted awaiting my return, but this is normal after an hiatus. My settlers got busy again once I came back, though, except whoever is in charge of upgrading the mill. Could my hiatus perhaps have triggered this bug?

nt

The thing is that I did visit once a day since Monday, but the 24-hour upgrade has still been taking much longer than it should.

You're sure you did not upgrade from level 4 to 5?

Ok, now I really feel stupid. You are right, Dilbe. I was sure it was only from level 3 to level 4, because of three things:

1) When I chose to upgrade it, I explicitly remember thinking "it's only a day".
2) I was certain I had only upgraded mines to level 4 or higher.
3) When I click on the building, it lists the material costs for the upgrade from level 4 to 5, which I thought was the next level.

So, ahem, yeah... :o Ok, move along, nothing to see here...