Bug: can't get into underground house...

[PZ]

... to complete the mission.

I received a mission to go to the veterinarian to pick up my malaria pills.  The underground house is near the water, and if you approach from the road, you have a high sniper position from which to attack.  When I peered down my scope, the mercs were all standing transfixed - they didn't move a muscle.  I killed them all (5 total) but the interact icon did not appear.  So, I left the area and allowed it to spawn - killed the same 5 guys and still no go.  Went the other way and attacked a GP, then returned to kill the same 5 guys - now the "Underground house unlocked" message appeared.  This was only the second time this has happened to me, and both times I had to leave to let the area spawn.  My advice: if this happens to you, keep trying, it should w@&k eventually, but you might need to go far, do another mission, or something else to hopefully get the program to respond correctly.

[Calibra88]

Yes all of the above is true.
Also please note that on some of the places you'll need to kill the patrol too.

[Art Blade]

cheers for that tip, Calibra88, and welcome to the forums :) 

[PZ]

Indeed Calibra88, this was an underground house with a roving Datsun patrol - never thought that he would need to be killed as well!  Thanks and welcome to OWG.