First up, this isn't an urgent bug. There's a really easy workaround, so this is doubly not an urgent bug. Closing and|or opening the build interface or selecting a different item to build circumvents the bug. Also, builds aren't blocked in any other squares. Even building in adjacent squares still works.
The save file has a Microbe Musher mid-deconstruction to make it easy to time the test.
Steps to Reproduce
Easiest way to show this bug:
1. Find a location that you can't place a building. (E.g. a building not yet deconstructed)
2. Try to place the building and take note of the square your cursor is over.
3. Wait for the build location to be valid without closing the build interface or selecting a different building
4. Attempt to place the building in the exact same square as before. (cursor can move between as long as you move it back)
This issue has not been confirmed by a developer yet.