Didn't saw a sticky for gameplay bugs, so I open this topic.
The tech bunker shown below on the fortress mode map "(6) Stronghold Prime" is completely surrounded and thus inaccessible for infantry at start.
One might of course be able to get rid of the sandbags with weapons or by driving over them, but since the other bunker above as well as the two on the other base entry can be directly entered, I'm sure this isn't intentional.