When I click a building's "finish for free" button, the time saved is not deducted immediately from the next building's finish time. I have to refresh the browser, then the finish time is calculated correctly.
You are correct in that the next building's cost of time is not affected by previous building's finish for free. But the next building's finish time should be pushed forward. This bug keeps the next building's finish time unchanged, but adds saved time to its cost time.
Ahh, that makes sense, the local machine isn't recalculating the complete time of the next building as it was just pushed up, and needs a refresh to display the correct time from the server. That should be easy to fix