Bug - Dam won't build

[HamsterDesTodes]

I'm playing as the Netherlands and while building a triple-city industrial complex I came across a strange bug. One of the dams I build to push the industrial districts adjacency bonus cannot be finished.
I locked it in a while ago, but now it won't let me finish. Neither building it in the city itself, nor using military engineers is possible.
While in the dam is visible in the city detail screen (and described as "under construction"), but the hexagon is greyed out in the citizen management screen.
it also wont stick when I try to produce it. The icon is there, but whenever I click it, the city just goes to the nothing-is-produced mode.

Anyone had such a problem before or an idea how to fix it?

[Grzemek]

If you preplace a Dam and reveal a strategic resource there before the Dam (or Canal to speak more generally) is completed, the game will never allow you to complete that Dam, and thus the whole river is messed up for you dam-wise until another civ completes it on that river. You can preplace other distrits on yet-to-be-revealed strategics just fine and delay the construction as much as you want, but Dams and Canals bug out.

[HamsterDesTodes]

Good (or to be more accurate: bad) to know, thanks!

[edit] yep, there is a niter below the dam. It would have been a +13 industrial district, ♥♥♥♥♥♥♥♥♥♥ :[