Check again on the common grounds issue. As long as there is no building on it, it should work now. With buildings, it should work as well if they are not common buildings (tower, well, etc.)
It allowed me to complete the turn with taking of common ground as actions this time, so would appear to be fixed.
If two people are trying to take the same plot, how about the chance for peasants to be killed? A home advantage if it's on land already owned by one of the families...
