Since today I can no longer build in 2 spots in sector 2:
These 2 spots had wheat fields which depleted. I can no longer build them back.
You can also see the remainder of the oad I had around the fields, which I removed. But I can not remove that part of the road.
If I try to place back the road, it wants to go around the mountain:
Other people don't seem to have the issue.
Building built there:
And others can build the road through that part of the mountain: